Desenvolvimento de aços sinterizados autolubrificantes a seco para a lubrificação sólida na...

Development of dry self lubricating sintered steels for solid lubrication in

mechanical engineering

Aloisio

N. Klein (Depto

de Eng. Mecânica LabMat/UFSC)

Mechanical Engineering DepartmentFederal University of Santa CatarinaFlorianópolis, Brazil

Materials Laboratory

Pesquisa Cientifica X Inovação tecnológica

O Brasil atualmente produz 2,18% dos artigos científicos do

mundo em revistas indexadas, mas o percentual de patentes

encaminhadas, que de certa forma representa um Índice de

Inovação

é

apenas da ordem de 0,02%.

Uma das maiores preocupações que temos hoje no BRASIL é aprender a utilizar a ciência para fazer tecnologia no Brasil e

tornar esta tecnologia em inovação no setor produtivo.

Na área de materiais, por exemplo, não basta desenvolver no

novo material. Para que ele venha a constituir de fato uma

inovação é

necessário que venha a ser homologado na produção

industrial, na forma de um componente com função de

engenharia especifica.

Inovação em Materiais

De uma forma geral, um problema crônico dificulta a rápida

incorporação de novos materiais e novos componentes em

sistemas mecânicos. Isto se deve a inexistência da infra- estrutura e até

de ampla metodologia para levar o processo

até

a fase de produto inovador disponível no mercado.

Para INOVAÇÃO definitiva, além do novo material

, é necessário:

projeto de componente;

prototipagem para testes no sistema;

produção de lotes em escala piloto de componentes

(alguns milhares) para a homologação do material, do

componente e do seu processo de fabricação.

Development of dry self lubricating sintered steels for solid lubrication in mechanical

engineering

Aloisio

N. Klein (LabMat/UFSC)

José

Daniel B. de Mello (LTM/UFU)Roberto Binder

(Whirlpool-EMBRACO)

Cristiano Binder

(LabMat/UFSC)Gisele Hammes

(LabMat/UFSC)

Renan Schroeder

(LabMat/UFSC)

Mechanical Engineering DepartmentFederal University of Santa CatarinaFlorianópolis, Brazil

Materials Laboratory

Authorship:

+

Most of the results shown in this presentation are part of a research program whose main goal is: -to develop dry self lubricating sintered steels that combine a low friction coefficient with high mechanical and wear resistance for applying in solid lubrication solutions.

Financial support:

Whirlpool/Embraco

(Joinville-Brazil) hermetic compressors producer (34 million compressors/year). (www.embraco.com.br)

Steelinject

(Caxias

do Sul

–

Brazil) sintered parts producer (powder injection molding)

(www.steelinject.com.br)

FINEP -

Financiadora

de Estudos

e Projetos

Brazilian

funding agency (www.finep.gov.br)

BNDES -

Banco

Nacional

de Desenvolvimento

Econômico

e Social ( www.bndes.gov.br

)

CNPq

-

Conselho

Nacional

de desenvolvimento

Cientifico

e tecnológico

( www.cnpq.br

). 5

6

Some general observations:

About 1/3 of all energy used in industrial countries goes to

overcome friction. High friction often results in high wear

and more than 30% of the production in industry goes to

replace worn out products with new ones.

A better control of wear would result in longer product

lifetimes and less energy consumption for replacement

production.

Thus, to reduce

friction and wear is

one

important path for reducing the energy consumption

and

decreasing the human impact on climate

change”

OUTLINEOUTLINE

1)

Introduction

2)

Brief overview on self lubricating sintered bulk materials

3)

Microstructure and materials requirements for high strength and high tribological

performance .

4)

Process, experimental and materials in development

5)

Some Results on sintered steels (MIM and die pressing)

6)

Conclusions

7

8

1) Introduction

9

In most tribological

applications, mainly fluid and grease lubricants are used to reduce friction and minimize wear;

But, there are several situations where the use of solid lubricant is the best way or even the only viable option:

1)

When working conditions become too severe the use of solid lubricants may be the only option

to reduce friction and to

control wear (e.g., high or low temperatures, low pressure or even in vacuum, or by extreme high contact pressure)

2)

In Microelectromechanical

Systems (MEMS);

3)

In appliances and small office equipment, such as printers, electric shavers, mixers, drills, cameras, etc.

10

A combination of solid and liquid lubrication is

also feasible and may have a synergistic effect in

reducing friction and wear of the contact

surfaces;

The solid lubricants can also be dispersed in

water, oil and grease to improve the friction and

wear under conditions of extreme pressure and /

or temperatures

Solid lubricant can be applied to mechanical parts in two ways:

1)

on the surface of the net shaped mechanical components in form of coatings (films ), or

2)

in the volume of the material as dispersed particles (bulk dry self lubricating composite materials)

1) Introduction

11

Solid lubricant

Solid lubricant can be applied to mechanical parts in two ways:

1)

on the surface of the net shaped mechanical components in form of coatings (films ), or

2)

in the volume of the material as dispersed particles (bulk dry self lubricating composite materials)

1) Introduction

12

Solid lubricant

Vapor deposition techniques (Chemical, Physical and Plasma assisted vapor deposition (CVD, PVD and PACVD))

Other coating technologies (lamellar solids)

Solid lubricant can be applied to mechanical parts in two ways:

1)

on the surface of the net shaped mechanical components in form of coatings (films ), or

2)

in the volume of the material as dispersed particles (bulk dry self lubricating composite materials)

1) Introduction

13

Vapor deposition techniques (Chemical, Physical and Plasma assisted chemical vapor deposition (CVD, PVD and PACVD))

Other coating technologies (lamellar solids)

Powder metallurgy techniques like:- die compaction - powder injection molding- powder extrusion- powder rolling, etc.

19

Powder metallurgy techniques are low cost serial mechanical parts manufacturing techniques

By processing the parts via powder metallurgy techniques, the composition of material can easily be tuned for the particular application.

20

21

SiC particles dispersed in Al: a) Mean particle size of SiC = 14,5 µm; b) Mean particle size of SiC= 1,5 µm

a b

22

UO2

+ 11Wt% Mo

23

Ni + 5%FeCr + 5FeP + 10%hBN

24

Powder metallurgy techniques are low cost serial mechanical parts manufacturing techniques

By processing the parts via powder metallurgy techniques, the composition of material can easily be tuned for the particular application.

Self lubricating bulk materials can re-generate its tribolayer after demage by wear or when even when it peels away (self healing effect)

Self healing effect of dry self lubricating sintered materials

Coefficient of friction

Load Electrical resistance of contact

Resistência elétrica do contato

25

OUTLINEOUTLINE

1)

Introduction

2)

Brief overview on self lubricating sintered bulk materials

3)

Microstructure and materials requirements for high strength and high tribological performance .

4)

Process, experimental and materials in development

5)

Some Results on sintered steels (MIM and die pressing)

6)

Conclusions

26

Solid lubricant particles dispersed in the volume

of the material

Porous bearings: Pores are lubricant

reservoirs (fluid lubricants and solid

lubricants27

2) Self lubricating sintered bulk materials

28

Dry self lubricating bearings:

Used for decades in households equipments and in office slight equipments (printers, electric shavers, drills, blenders, among others)

Solid lubricants phases mostly used include:

•

graphite, hexagonal boron Nitride (h-BN), molybdenum disulfide (MoS2

), tungsten disulfide (WS2

) and other dichalcogenides (lamellar solids)

•

Low melting metals (silver, tin, lead, others), halides, oxides, among others.

The most used metallic matrixes are:

copper alloys, ferrous alloys and nickel alloys.

2) Self lubricating sintered bulk materials

29

Usually these materials have a high content of solid lubricant (15 to 35 v/o). This results in a high degree of discontinuity of the metallic matrix leading to poor mechanical strength of composite.

Thus, these materials cannot be used for a lot of typical mechanical applications where we need higher mechanical and wear resistance of the self lubricating sintered material.

So we need to develop bulk dry self lubricating materials that combine a low friction coefficient with high mechanical strength, tuned for each particular application

OUTLINEOUTLINE

1)

Introduction

2)

Brief overview on self lubricating sintered bulk materials

3)

Microstructure and materials requirements for high strength and high tribological performance .

4)

Process, experimental and materials in development

5)

Some Results on sintered steels (MIM and die pressing)

6)

Conclusions

30

1)

optimization of microstructure parameters of the composite material (content of solid lubricant,

lubricant particle size and size distribution, mean free path between lubricant particles)

By designing dry self lubricating composites with improved mechanical properties and low friction coefficient, we have to consider some specific requirements :

3) Microstructure and materials requirements for high strength and high tribological performance

Binder, C.; Hammes, G.; Schroeder, R.; Klein, A. N. ; De Mello, J.D.B.; BInder, R. ; Ristow Jr, W. . “Fine tuned”

steels point the way to a

focused future. Metal Powder Report, v. 65, p. 29-37, 2010.31

32

“regular distribution each particle has to provide lubricant for a well defined area of the interface”.

Ideal situation -

model

Area on thesurfaces to be lubricated by each lubricant

particle

Solid lubricant particles

dispersed in the composite

material

3) Microstructure and materials requirements for high strength and high tribological performance

1)

optimization of microstructure parameters of the composite material (content of solid lubricant,

lubricant particle size and size distribution, mean free path between lubricant particles)

2)

mechanical properties of the metallic matrix tuned for specific application (hardness, strength and toughness)

By designing dry self lubricating composites with improved mechanical properties and low friction coefficient, we have to consider some specific requirements :

Binder, C.; Hammes, G.; Schroeder, R.; Klein, A. N. ; De Mello, J.D.B.; BInder, R. ; Ristow Jr, W. . “Fine tuned”

steels point the way to a

focused future. Metal Powder Report, v. 65, p. 29-37, 2010.

3) Microstructure and materials requirements for high strength and high tribological performance

33

The metallic matrix of the composite must be hard enough

to avoid occurrence of micro plastic deformation by friction

and wear under operation. The mass flow of plastic

deformation covers gradually the lubricant particles,

breaking replacement of lubricant to the interface.

3) Microstructure and materials requirements for high strength and high tribological performance

34

OUTLINEOUTLINE

1)

Introduction

2)

Brief overview on self lubricating sintered bulk materials

3)

Microstructure and materials requirements for high strength and high tribological performance .

4)

Process, experimental and materials in development

5)

Some results withn sintered steels (MIM and die pressing)

6)

Conclusions

35

36

1)

mix particles of solid lubricant with the metal matrix powders by any mixing process

2)

generate particles of solid lubricant “in situ”

during the sintering by reaction between components (for example, dissociation of a carbide).

There are two different ways to get solid lubricant particles dispersed in the volume of the matrix:

Binder, C.; Hammes, G.; Schroeder, R.; Klein, A. N. ; De Mello, J.D.B.; BInder, R. ; Ristow Jr, W. . “Fine tuned”

steels point the way to a focused

future. Metal Powder Report, v. 65, p. 29-37, 2010.

3) Microstructure and materials requirements for high strength and high tribological performance

Undesirable distribution

(Iron + Graphite) powder mixture(after sintering)

(Iron + h-BN) powder mixture(after sintering)

Mixing process: mechanical stresses leads to spreading of lamellar solid lubricant by shearing

50 m50 m

solid lubricant phase

We need solid lubricant nodules with rounded shape in order to avoid stress concentration.

37

3) Microstructure and materials requirements for high strength and high tribological performance

Shape and distribution of h-BN dispersed in nickel alloys after sintering: a) Ni + 10%hBN ; b) Ni + 5%FeCr (wt%) + 5%FeP(wt%) + 10%hBN (vol%).

b) Liquid phase assisted sintering

a) Sintering without liquid phase

38

Method used for the measurement of the length of segments along the matrix phase.

39

20m

Mean free path lengths between solid lubricant particles along the matrix [m]

Fre

quen

cy o

f occ

urre

nce

[%]

0

5

10

15

20

25

0 50 100 150 200

Ni + 10%hBN (without liquid phase)

Ni + 10%hBN + 5%FeCr + 5%FeP (liquid phase sintering)

Mean free paths lengths between solid lubricant particles measured along matrix of sintered composite material. a) Sintering without liquid phase; b) Sintering in presence of liquid phase.

m

= 19,5

1,6 m

m

= 65,5

4,8 m

40

41

1)

mix particles of solid lubricant with the metal matrix powders by any mixing process

2)

generate particles of solid lubricant “in situ”

during the sintering by reaction between components (for example, dissociation of a carbide).

There are two different ways to get solid lubricant particles disperse in the volume of the matrix:

Binder, C.; Hammes, G.; Schroeder, R.; Klein, A. N. ; De Mello, J.D.B.; BInder, R. ; Ristow Jr, W. . “Fine tuned”

steels point the way to a

focused future. Metal Powder Report, v. 65, p. 29-37, 2010.

3) Microstructure and materials requirements for high strength and high tribological performance

g(T)sol

= nA

RTlnaA

+ nB

RTlnaB

+ ... +

nM

RTlnaM

(1)

Example: Will compound AB dissociate ain a matrix M ? In this case we have to compare the values for Gibbs free energy for formation of solid solution between A

and B at temperature T

(equation 1), and the Formation Gibbs free energy of compound AB at the same temperature T (equation 2) .

G0(T)AB

= C1

+ C2

TlogT + C3

T (2)

Dissolution will occur up to activity values (corresponding to concentrations values via relation ai

= xi

i

) for which relation 3 is satisfied: |AG(T)sol

|

≥

|G0(T)AB

|

g(T) = [nA

RTlnaA

+ nB

RTlnaB

+ nM

RTlnaM

] -

nG0T

(AB)

Using thermodynamic data for selecting the mixture components

42

(3)

1,0 0,1 0,01 0,001 0,0001

G0(T)TiC

G0(T)NbC

G0(T)Cr4C

- 10

- 20

0

- 30

- 40

- 50

Activity of alloying element Si dissolved in the matrix

G0 (

T) a

t 115

00 C [k

cal/

mol

]

RTlnaSi

RT lnaSi = G0(T)SiC

T = TS = 1150 OC

G0(T)SiC

G(T) = [nSi

RTlnaSi

+ nC

TlnaC

+ nM

RTlnaM

] -

nG0T

(SiC)

Example: Silicon carbide (SiC) in Iron, 11500C

43

+ 10

0

- 10

- 20

- 30

- 40

- 50 0 200 400 600 800 1000 1200 1400 1600

Temperatura (0C)

3/2Cr + C = 1/2Cr3C2

Mn + C = MnC

[ T(0K) = T(0C) + 273 ]

G0 (T

)kc

alm

ol

[

[

44

45

a)

Powder injection moulding (fine carbonyl powders)

Self lubricating sintered steels : Fe + C + SiC + Ni + Mo alloy system;

Self lubricating composites with Ni alloys as matrix

Solid lubricants used: h-BN, Graphite and mixtures of them

b)

Uniaxial die pressing (atomized powders from Höganäs)

Self lubricating sintered steels : Fe + C + SiC + Ni + Mo alloy system;

Solid lubricant used: h-BN, Graphite and mixtures of them

Test samples production

a

a)

Fe + 0.6%C + 4%Ni

Ferrite + perlite

b) Fe + 0.6%C + 4%Ni + 2%SiC Ferrite + Perlite + Graphite

nodules that are surrounded by a ferrite ring

Sintered steels produced by MIM (sintered in the PADS

furnace, TS

= 1150 C, 1h, H2

)

b

Solid lubricant nodules formed “in situ”

during the

sintering by dissociation of SiC

46

47

Line profile -

Microprobe analysis

graphitenodule

FEG-SEM image

of an graphite nodule (taken on a fractured surface)

48

FEG-SEM image of the interior of the graphite nodule: Graphite foils with 10 to 45 nm in thickness (about 30 to

100 atom planes)

49

Fe+0,6C+ 3SiC+4Ni Fe+0,6C+ 3SiC+4Ni+1Mo

Microstructure of Fe+C+SiC+Ni+Mo steels (1h, 1150C, H2

plasma assisted)

Fe + 0,6C + 3SiC Fe+0,6C+2SiC+4Ni

51

Graphite nodules formed “in situ”

during the sintering:

Tensile strength = 710 Mpa

Friction coefficient

= 0,06

3) Microstructure and materials requirements for high strength and high tribological performance

50 m50 m

solid lubricant phase

Sintered steel graphite as solid lubricant mixed to the feedstock

Tensile strength = 340 Mpa

Friction coefficient

= 0,11

20 m

Solid lubricant nodules

OUTLINEOUTLINE

1)

Introduction

2)

Brief overview on self lubricating sintered bulk materials

3)

Some considerations about microstructure and properties requirements.

4)

Process, experimental and materials in development

5)

Some Results on sintered steels (MIM and die pressing)

6)

Conclusions

52

4)Mechanical and tribologycal properties of dry self lubricating sintered MIM steels

53

1) Powders

Fe BASF (CL-OM)

carbonyl iron powder with a mean particle size of 7.8 m;

Mo elemental Mo (OMP HC Starck, d (mean) = 5,5 m,)

Ni element Ni powder (INCO 123, d (mean) = 8,86 m);

SiC

mean particle size of 10 m

2) Feedstock preparation

The feedstock for injection molding was prepared by mixing the powder (Haake Sigma mixer, 180C, 70 rpm, 90 min) with 8% (w/o) organic binders (binder system)

Binder system:

paraffin-wax, stearic acid (surfactant), amide wax,

EVA (ethylene vinyl acetate copolymer) and polypropylene (back bone). 54

4) A chemical debinding step

dissolution of the low molecular weight components of the binder system in hexane.

5) Thermal Debinding

and

Sintering (1100 to 1200 C, 1h, H2

plasma (low energy)

The thermal debinding, as well as the sintering , were performed in the same thermal cycle in a Hybrib Plasma Plasma ReactorReactor,

i.e., using the Plasma Assisted Debinding and

Sintering (PADS) process develop in Brazil.

3) Injection of the parts Arbourg 320S injection molding machine (pressure: 100 MPa).

55

Plasma Assisted Debiding (PAD)(using the reactive environment of a plasma)(using the reactive environment of a plasma)

Electron bombardment ofmacromolecules (inelastic collision)

Macromolecule dissociation

C C C C C C

HH H H H H

H H H H H H

n

polyethylene

H

C

H

H

C

H

H

C

H

H

C

H

H

C

H

C

H

H

C

H

HHH

HH

HH

HH

HH

HH

HHHH

A. N. Klein et all, US Patent Nr. US 6,579,493 B1 (2003)

A. N. Klein at all, European Patent No. EP 1 230 056 B1 (2003)

e + He + H

22

= H + H + e= H + H + e

56

vacuum chamber

energy supply for electrical heating

energy supplyfor the cathode

cathode

gas inlet

anode

electrical heating elements

thermocouples

vacuum system

Shielding

cooling system

Design (schematic) of the hybrid plasma DC reactor 57

Plasma Reactor: Pilot Plant at LabMat

R. Machado, A. N. Klein, …

“Industrial Plasma Reactor for Plasma Assisted Thermal

Debinding of Powder Injection-Molded Parts. US 7,718,919 B2 (2010) 58

Mechanical Engineering DepartmentFederal University of Santa CatarinaFlorianópolis, Brazil

Materials Laboratory

anode

cathode

Al2

O3

plate

Plasma Assisted Debinding and SinteringPlasma Assisted Debinding and Sintering (PADS) (PADS) in the same thermal cyclein the same thermal cycle

60

After debinding After debinding without without plasmaplasma: organic residues remain in the reactor: organic residues remain in the reactor

61

After debinding After debinding withoutwithout plasmaplasma: details of organic residues : details of organic residues

62

Processing time (h)

Tem

pera

ture

(0 C)

debinding plasma nitriding or carbonitriding

Debinding and sintering in the same equipment Debinding and sintering in the same equipment and same thermal cycleand same thermal cycle (single (single –– cycle)cycle)

sintering

Saving energy and processing

time!

63

Steelinject Industrial PADS Equipment Steelinject Industrial PADS Equipment

Properties of Fe + 0,6%C

+ SiC sintered steels

65

0

500

1000

1500

2000

2500

3000

3500

0,00

0,05

0,10

0,15

0,20

0,25

0,30

0,35

0,40

0,45

0,50

0 1 2 3 4 5

Fric

tion

Coe

ffici

ent

SiC Content (w/o)

Friction Coef f icient Durability

Dur

abili

ty (

N.m

)

Fe + 0.6%C + SiC

sintered steels (1150 C, 1h, H2

, PADS)66

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0 1 2 3 4 5 6

Fric

tion

Coe

ffici

ent

SiC content ( % )

1100 °C

1150 °C

1200 °C

Friction coefficient as a function of sintering temperature

Fe + 0,6%C + SiC sintered steels (1h, H2

, PADS)

67

Mudar graficos

0

2

4

6

8

10

12

14

16

0 1 2 3 4 5 6SiC content ( % )

Scuf

fing

Res

istan

ce (

N.m

)103

1100 °C

1150 °C

1200 °C

68

De Mello & Klein. To be published69

Comparison of friction coefficient of materials containing distinct graphite types

Tensile strength, hardness and elongation measured on the sintered Fe + 0.6%C + increasing content of SiC (w/o).

0

3

6

9

12

15

18

0

100

200

300

400

500

600

700

800

0 1 2 3 4 5

Elo

ngat

ion

(%)

Yiel

d S

treng

th a

nd T

ensi

le S

treng

th(M

Pa)

Har

dnes

s (H

V)

SiC Content (w/o) in matriz Fe + 0.6C

HV 0,2 YS UTS % EL

SiC content (w/o) in the Fe + 0,6%C matrix

70

Properties of Fe + 0,6%C + Ni + Mo + SiC

sintered steels

71

Martensitic dry self lubricating sintered steels. Fe + 0,6C + 4Ni + 1Mo + 3SiC

Mechanical properties of some of sintered self lubricating steels

73

HV = 400UTS = 810 MpaElongation = 6%

74

75

Wear bahavior in sliding tests

Conclusions

1)

Self lubricating sintered steels produced by Powder Injection Molding with a wide range of mechanical properties (200-1000 MPa and 150-600HV) were obtained. The friction coefficient of this materials can be varied in a range from

= 0,04 to

= 0,21

2)

Compositions having at the same time Ni, Mo, Si and C generate a martensitic microstructure even under low cooling rates.

3)

It is suggested that graphite foils, removed from the “in situ” generated graphite nodules, remain at the interface, thus

contributing to the formation of the protective tribolayer.

76

Thanks for your attention!

77

Fe+0.6%C+3% SiC

Graphite

Fe3

CFe Fe

Fe

Angle

Inte

nsit

y

Dissociation of SiC in iron matrix

78

Fe+0.6% C+3% SiC Fe+0.6% C+3% SiC ––

1100 1100 °°C C

0 20 40 60 80 100 120

200

400

600

800

1000

1200

1400

1600

1800

2000

2200

2400In

tens

idad

e

2(Graus)

240 min 120 min 60 min 30 min 10 min

Graphite

Fe3

C Fe Fe

Fe

Angle

Inte

nsit

y

In situ dissociation of precursorIn situ dissociation of precursor

79

Martensitic dry self lubricatiing sintered steels. Fe + 0,6C + 4Ni + 1Mo + 3SiC (verificar na tese cristiano

81

Self healing effect of the dry self lubricating sintered steel produced (composite material)

82

(a) (b)Reciprocating wear test (un-lubricated, in air). (a) equipment; (b) steel sphere (held on a pivoted arm) compressing against the

moving specimen surface (schematically)

5) Tribological characterization

2) Materials and experimental

500 1000 1500 2000 2500 3000

Raman shift / cm-1

0

1000

2000

3000

4000

5000

Cou

nts

1581.65

2727.42

Graphite powder UF4

500 1000 1500 2000 2500 3000

Raman shift / cm-1

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

Cou

nts

1356.62

1582.3

2727.11

Graphite nodulenodular cast iron

Graphite noduleGraphite noduleSiC dissociationSiC dissociation

D b

and

(sp3

-dia

mon

d)

Graphite noduleSiC dissociation

Raman Spectroscopy

G’Ba

nd

G b

and

(sp2

–gr

aphi

te)

full-width at half peak height

83

MaterialBand D position

(cm-1)

Band G position

(cm-1)

Band D FWHPH

(cm-1)

Band G FWHPH

(cm-1)ID / IG

Crystallite size La

(Å)

Band G’ Position (cm-1)

Band G’ Shape

Graphite powder

1354.34 1581.65 8.0 14.71 0.050 880.00 2726,80Broad

Nodular cast iron

1356.62 1582.3 16.50 27.96 0.189 232.80 2727,10Broad

Fe+0.6C+3SiC 1351.55 1586.60 58.97 42.22 1.183 37.19 2709,17Peak

FWHPH-

full-width at half peak height

De Mello & Klein et al, 64th STLE Annual Meeting, Las Vegas, 2010

Turbostratic 2D graphite Higher interlamellar distances Lower friction coefficient

84

Results and discussionResults and discussion: : Tribological behaviourTribological behaviour

Fe+0.6%C+5%SiC, 14 N

It is reasonable to suppose that the graphite foils are removed from the in situ generated graphite nodules and remain at the interface thus contributing

to the formation of the protective tribo-layer;

On the other hand, the tribo- layers also degrade under the

sliding action.

Wear track

85

Fe

+ 0.6%C + 5%SiC(14 N, 11500C,1h,PADS)

500 1000 1500 2000 2500 3000

Raman shift / cm-1

0

1000

2000

3000

4000

5000

6000

7000

8000

Cou

nts

1350.15

1582.08

2698.25

2939.84

Wear scar

Before test

Turbostratic 2D graphite

Higher interlamellar

distances

Low friction coefficient

86

The Plasma Assisted Debinding

rate is a function of several variables:

type of polymer or binder system used (properties of the binders)

temperature and heating up rate (time)

energy and quantity of the reactive species generated in the plasma.

We need electrons with enough energy to cause the dissociation of de binder molecules, and

Atomic Hydrogen (H2

+ e = H + H + e ).

The reaction constant for any dissociation reaction promoted by energy transfer via inelastic collisions of electrons with binder molecules in the plasma may be given by

0

)()( dgK eer

Wherein:

)(eg energy distribution function of the electrons

)( e cross section of collision distribution function (cross section for the inelastic collision which promote the dissociation), as a function of the electrons energy

UFSCUFSC-- Mechanical Engineering DepartmentMechanical Engineering DepartmentMATERIALS LABORATORY MATERIALS LABORATORY

Team involved in the developments:Team involved in the developments:Joel L. R. Joel L. R. MuzartMuzart††,,

Antonio R. de Souza,Antonio R. de Souza,

Carlos Carlos SpellerSpeller, Ana M. , Ana M. MaliskaMaliska, Paulo , Paulo

A. P. A. P. WendhausenWendhausen, Marcio C. , Marcio C. FredelFredel, Cristiano , Cristiano BinderBinder, Davi Fusão, Roberto , Davi Fusão, Roberto BinderBinder, , WaldyrWaldyr

RistowRistow

Jr., Ricardo Machado, Paulo Alba, Maria A. dos Santos, Jr., Ricardo Machado, Paulo Alba, Maria A. dos Santos,

Rubens M. do Nascimento, Wagner da Silveira, Henrique C. Rubens M. do Nascimento, Wagner da Silveira, Henrique C. PavanatiPavanati, Gisele , Gisele HammesHammes, Vilson J. Batista, Ivani T. , Vilson J. Batista, Ivani T. LawallLawall...)....).

AloisioAloisio

N. KleinN. Klein

Plasma technology applied to powder Plasma technology applied to powder materials processingmaterials processing

1) 1) Plasma technology applied to powder materials Plasma technology applied to powder materials processingprocessing

c)c) ThermoThermo--chemical surface treatments chemical surface treatments -- via plasmavia plasma(cleaning, nitriding, cementation,…)

a) a) Plasma Assisted Plasma Assisted DebindingDebinding and Sintering (PADS)and Sintering (PADS) of PIM partsof PIM parts(dissociation of organic macromolecules)

b)b) Plasma Assisted Sintering: Surface modification via plasmaPlasma Assisted Sintering: Surface modification via plasma(surface morphology, chemical composition / surface enrichment ,cathodic sputtering, …).

OUTLINEOUTLINEOUTLINE

Plasma generation(abnormal DC glow discharge)

luminescent region

Cathode Anode

reactive species

- V

- V

++

00++

--

heat generation and sputtering

2) Inelastic collision

of

electrons with gaseous species in the plasma environment:

chemical reactions improvement

Important phenomena in the plasma environment:

1) Ionic and fast neutral atoms bombardment on the cathode:

Vp

1) 1) Plasma technology applied to powder materials Plasma technology applied to powder materials processingprocessing

c)c) ThermoThermo--chemical surface treatments chemical surface treatments -- via plasmavia plasma(cleaning, nitriding, cementation,…)

a) a) Plasma Assisted Debinding and Sintering (PADS)Plasma Assisted Debinding and Sintering (PADS) of PIM partsof PIM parts(dissociation of organic macromolecules)

b)b) Plasma Assisted Sintering: Surface modification via plasmaPlasma Assisted Sintering: Surface modification via plasma(surface morphology, chemical composition / surface enrichment ,cathodic sputtering, …).

OUTLINEOUTLINEOUTLINE

Plasma Assisted Debiding (PAD)(using the reactive environment of a plasma)(using the reactive environment of a plasma)

Electron bombardment ofmacromolecules (inelastic collision)

Macromolecule dissociation

C C C C C C

HH H H H H

H H H H H H

n

polyethylene

H

C

H

H

C

H

H

C

H

H

C

H

H

C

H

C

H

H

C

H

HHH

HH

HH

HH

HH

HH

HHHH

A. N. Klein et all, US Patent Nr. US 6,579,493 B1 (2003) A. N. Klein at all, European Patent No. EP 1 230 056 B1

(2003)

e + H2 = H + H + ee + H2 = H + H + e

b) The furnace remains clean

possibility for debinding and sintering in the same equipment in a single – cycle

Plasma Assisted Debinding of PIM parts

Advantages:

a) Increasing of the debinding rate

save processing time / improve the productivity

1)

Electrons impinging the surface of the parts causes dissociation of binder molecules to convert the binder into gas

molecules

2) A new portion of the molted binder flows up to the top via interconnected pores reducing the time needed for binder removal

Plasma Assisted DebindingPlasma Assisted Debinding

0 10 20 30 40 50 60

0

50

100

Po

lypr

opyl

ene

rem

oval

(%)

Time (min)

Anode-cathode Floating potential Anode/shield-cathode

Plasma Assisted Debinding: Plasma Assisted Debinding: Effect of the electrons on the debinding rateEffect of the electrons on the debinding rate(Experimental Results for Polypropylene in (Experimental Results for Polypropylene in hydrogen electrical discharge)hydrogen electrical discharge)

T = 400T = 400°°CC

Plasma Reactor: Pilot Plant at LabMat

R. Machado, A. N. Klein, …

“Industrial Plasma Reactor for Plasma Assisted Thermal

Debinding of Powder Injection-Molded Parts. US 7,718,919 B2 (2010)

After After Plasma Assisted DebindingPlasma Assisted Debinding: no organic residues : no organic residues remain in the reactorremain in the reactor

anode

cathode

Al2O3 plate

Parts after Parts after Plasma Assisted Debinding and SinteringPlasma Assisted Debinding and Sintering (PADS) (PADS) in the same thermal cyclein the same thermal cycle

Parts after Parts after Plasma Assisted Debinding and SinteringPlasma Assisted Debinding and Sintering (PADS) (PADS) in the same thermal cyclein the same thermal cycle

After debinding After debinding without without plasmaplasma: organic residues remain in the reactor: organic residues remain in the reactor

After debinding After debinding withoutwithout plasmaplasma: details of organic residues : details of organic residues

Processing time (h)

Temperature (0C)

debinding plasma nitriding or carbonitriding

Debinding and sintering in the same equipment Debinding and sintering in the same equipment and same thermal cycleand same thermal cycle (single (single –– cycle)cycle)

Sintering

Some resultsSome results

--

Fe+ 2Ni + 0,6C low alloy steel Fe+ 2Ni + 0,6C low alloy steel

--

316316--L stainless steel.L stainless steel.

Binder system:

polymer and wax. Wax debinding: organic solvent.

Thermal debinding and sintering: PADS furnace.

Alloy Debinding parameters

Sintering parameters

2NiFe0,6C(carbonyl powders)

Heating rate: 2,0 ºC/min.

Atmosphere: atomic hydrogen

1250 ºC, 60 min, argon partial

pressure

316-L(atomized powders)

1300 ºC, 90 min, H2 partial pressure

AlloyAlloy ConditioConditio nn

ProcesProces ss

DensitDensit y y

(g/cm(g/cm33))

Carbon Carbon content content

(% mass)(% mass)

Hardness Hardness (HV 0,2 (HV 0,2

kg)kg)

Ultimate Ultimate Strength Strength

(MPa)(MPa)

Yield Yield StrengtStrengt h (MPa)h (MPa)

ElongElong ation ation (%)(%)

Fe + Fe + 2% Ni 2% Ni + 0,6C+ 0,6C

sinteredsinteredPADSPADS 7,657,65 0,58 0,58 ––

0,620,62 170170 575575 480480 44

Conv.Conv. 7,507,50 0,6 0,6 –– 0,80,8 160160 500500 250250 33

temperedtemperedPADSPADS 7,657,65 0,58 0,58 ––

0,620,62 350350 12101210 11801180 22

Conv.Conv. 7,507,50 0,6 0,6 –– 0,80,8 340340 950950 800800 33

316316--LL sinteredsinteredPADSPADS 7,707,70 0,00150,0015 170170 505505 290290 5454

Conv.Conv. 7,857,85 0,03 m0,03 mááx.x. 120120 510510 180180 5050

Comparison of metallurgical variables of materials processed in PADS furnace and in a conventional route (catalytic

debinding)

PADS process x LupatechPADS process x Lupatech’’s actual processs actual process

ProcessProcess Lead time Lead time (h)(h)

Heating rate Heating rate during debinding during debinding

((ººC/min)C/min)

Energy Energy consumption consumption

(kW)(kW)

Gas Gas consumption consumption

(m(m33))

PADSPADS 77 2,02,0 500500 1212

LupatechLupatech 8080 0,070,07 800800 120120

Processed alloy: 316Processed alloy: 316--L stainless steel:L stainless steel:

–

Actual process: permeation controlled thermal + vacuum sintering.

–

PADS process: Plasma Assisted Debinding and Sintering.

Steelinject Industrial PADS Equipment Steelinject Industrial PADS Equipment

Industrial Plasma Reactor for Plasma Assisted Thermal Debinding of Powder Injection-Molded Parts. US Patent Office, number US 7,718,919 B2 (2010)

113

Resultados:Resultados:

Redução de custo (processo PADS): mínimo 20 %

Redução de energia (processo PADS): : 50%

Premio Medalha de desenvolvimento

114

Nestor Perini

http://medalha.desenvolvimento.gov.br/arquivos/agra ciados06.htm

Cargo: Presidente da Lupatech S/A

Indicação: Sr. Paulo Belini; Sr. Jorge Gerdau Johannpeter e Sr. Raul Anselmo Randon

Justificativa da

Indicação:

A Lupatech S/A., através de sua divisão Steelinject, é pioneira na América Latina na utilização da tecnologia MIM (Metal Injection Molding). Esta tecnologia é indicada para produção de peças em série de alta precisão e complexidade de forma. A Steelinject conseguiu reduzir em 20% os custos de produção e em 50% o de consumo de energia graças a uma tecnologia desenvolvida em parceria com o laboratório de materiais da Universidade Federal de Santa Catarina (UFSC). Com o invento, a empresa pretende deixar de ser importadora para se tornar exportadora de tecnologia. A patente nos Estados Unidos acabou de ser registrada e está em processo o registro na Europa. No Brasil, a patente já está no Instituto Nacional de Propriedade Industrial (INPI).

115

Processo de transferência da Processo de transferência da tecnologia para PADS para USAtecnologia para PADS para USA

Lupatech (Caxias)

+ LabMat (UFSC)

DSH Technologies, LLC, que através da associada -

Elnik

Systems vai produzir o equipamento e disponibilizar no mercado mundial.Primeiro equipamento em 3D foi exposto na PM2008 em Washington

(8 a 12 de Junho )

Forno PLASMIM projetado para a Empresa Elnik Systems (USA) pela Equipe do LabMat/UFSC + Steelinject (Caxias do sul)

Protótipo Forno Hibrido para extração térmica de ligantes orgânicos assistida por plasma seguida de sinterização assistida por plasma.

Possibilities:Possibilities:

A) Plasma reactor with an auxiliary resistive heatingA) Plasma reactor with an auxiliary resistive heating

B) Plasma reactor without auxiliary resistive heatingB) Plasma reactor without auxiliary resistive heating

The plasma is used only to promote the chemical reactions. Plasma works with low current density (at the exact current needed).

Heat is generated by the plasma, i.e., only by the bombardment of the cathode by ions and atoms of high energy.

Problem:Problem: high sputtering from cathode – surfacecontamination

Opportunity:Opportunity: this can be used for surface enrichment of unalloyed iron parts

Plasma reactors for materials processingPlasma reactors for materials processing

Modification of the chemical composition of parts during plasma assisted sintering

Surface enrichment of unalloyed iron with Chromium

0 5 10 15 20 25 300

1

2

3

4

5

6C

once

ntra

ção

de M

o (%

peso

)

Profundidade (m)

1150 °C 1000 °C 800 °C

Enrichment with Molybdenum: Temperature Influence Enrichment with Molybdenum: Temperature Influence (1Torr;(1Torr;

700V; 1h ; 700V; 1h ;

10%H2 + 90%Ar; Gas flow = 5 x 1010%H2 + 90%Ar; Gas flow = 5 x 10--66

mm33/s (300 sccm)/s (300 sccm)

Conc

entr

atio

n of

Mo

(%w

eigh

t)Co

ncen

trat

ion

of M

o (%

wei

ght)

Depth(Depth(µµm) m)

0 10 20 30 40 50 60 70 80 90 1000

1

2

3

4

5

6

7

8

Con

cent

raçã

o de

Mo

(%pe

so)

Profundidade (m)

3,5 Torr 1 Torr

Conc

entr

atio

n of

Mo

(%w

eigh

t)Co

ncen

trat

ion

of M

o (%

wei

ght)

Depth(Depth(µµm) m)

Enrichment with Molybdenum: Pressure Influence Enrichment with Molybdenum: Pressure Influence ( ( 1150 1150 °°CC

; ; 700V; 1h ; 10%H2 + 700V; 1h ; 10%H2 +

90%Ar; Gas flow = 5 x 1090%Ar; Gas flow = 5 x 10--66

mm33/s (300 sccm)/s (300 sccm)

800800°°C; 500 V C; 500 V

800800°°C; 700 V C; 700 V

Deposition of atoms/ions sputtered from the Deposition of atoms/ions sputtered from the cathode (clusters of size in the nanometer range)cathode (clusters of size in the nanometer range)

0,0 0,2 0,4 0,6 0,8 1,00

50

100

150

200

250

Con

tage

m

Tamanho de partícula (m)

500 V 700 V

Am

ount

Am

ount

Particle size (Particle size (µµm)m)

View of the lateral side which is exposed to ion bombardment

Base, which is in contact to the support and does not receive bombardment

Ion bombardmentIon bombardmentSputtering +Sputtering +

deposition anddeposition and

activated diffusionactivated diffusion

Dense surface layerDense surface layer

Surface dense layer in plasma assisted sintering Surface dense layer in plasma assisted sintering (parts placed on the cathode)(parts placed on the cathode)

The International Journal of Powder Metallurgy, Vol. 34, No. 8, 1998, pg.55–62.

Ionic bombardment of the surface improves diffusion rates;

As compactedAs compacted Afther sintering (on cathode)Afther sintering (on cathode)

Sintering of unalloyed iron samples produced by powder compaction

The densification is further enhanced by the The densification is further enhanced by the retrodeposition of atoms.retrodeposition of atoms.

Surface dense layer in plasma assisted sintering Surface dense layer in plasma assisted sintering (parts placed on the cathode)(parts placed on the cathode)

1) 1) Plasma technology applied to powder materials Plasma technology applied to powder materials processingprocessing

c)c) ThermoThermo--chemical surface treatments chemical surface treatments -- via plasmavia plasma(cleaning, nitriding, cementation,…)

a) a) Plasma Assisted Debinding and Sintering (PADS)Plasma Assisted Debinding and Sintering (PADS) of PIM partsof PIM parts(dissociation of organic macromolecules)

b)b) Plasma Assisted Sintering: Surface modification via plasmaPlasma Assisted Sintering: Surface modification via plasma(surface morphology, chemical composition / surface enrichment ,cathodic sputtering, …).

OUTLINEOUTLINEOUTLINE

Unalloyed iron: sintering followed by plasma nitriding

20 m 20 m

NITRIDE LAYERNITRIDE LAYER

Surface and Coatings Technology 141(2001) 128-134

c)c) ThermoThermo--chemical surface treatments chemical surface treatments -- via plasmavia plasma(nitriding, cementation, nitro cementation)(nitriding, cementation, nitro cementation)

Montagem parcial da carga a ser tratada.

Reator de nitretação por plasmaescala piloto (4 mil peças por

carregamento)

127

Desenho esquemático célula de limpeza e nitretação –

escala industrial 4,5

milhões peças/ano

Remoção do óleo de calibração dos poros residuais e nitretação por plasma de materiais sinterizados em único ciclo térmico (patente);

128

Foto da célula em operação na Empresa GKN (fornecedor de peças para a Embraco)

Remoção do óleo de calibração dos poros residuais e nitretação por plasma de materiais sinterizados em único ciclo térmico (patente);

129

Foto da célula em operação na

Empresa GKN (fornecedor de

peças para a Embraco)