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Felületmódosítás
Korszerű anyagok és technológiák, MSc
2013
A felületi tulajdonságok tudománya: átfogó (interdiszciplináris) terület
• A felület a tiszta fizikai és kémiai tulajdonságok szemszögéből.• Topográfiával kapcsolatos tulajdonságok (felületi érdesség).
• Tágabb értelemben: „surface engineering”: komplex nézőpont• Kapcsolat a felületi tulajdonságok, az alkalmazás és az
alkalmazott technológiák között.
• (Tiszta fizikai és kémiai tulajdonságok: alapkutatás szemszöge.)
• A felületek tulajdonsága a felhasználók szempontjából: „surface engineering”.
Kondenzált anyagok nagy fajlagos felülettel:a „komplexitás” alapja a felület
• Felületi tulajdonságok kialakulása ← klaszterek tulajdonsága (mérethatás):
• „Méretfüggő” tulajdonságok: átmenet az önálló atomtulajdonságok és a termodinamikailag stabil makroszkópos tulajdonságok között;
A redukált ionizációs energia különböző szabadfelületű fémklaszterek esetében a klaszterátmérő reciprokának függvényében
Aim: the local modification of surface properties changing either the local composition or the structure or both of them.
The desired surface properties are often contradict to those in the bulk! (i.e. local hardness, local corrosion resistance)
examples: development of peculiar compositional relations on the surface of semiconductors
The development of hard, wear- or corrosion-resistant surfaces on cutting, drilling tools
Development of optical or decorative layers
Two alternatives:Covering the surface with protective layer (corrosion resistant layers)Structural or compositional changes in the surface layer
Traditional methodsIncrease of non-metallic element concentration in the surface layer, using heterogeneous reaction.i.e. iron/steel heating in appropriate gas-mixture (carbonization, decarbonization, nitridation)
CH4 [C]Fe + 2H2 CH4/H2
2NH3 [N]Fe + 3H2 NH3/H2
Layer deposition using electrochemical or chemical methods Hard chromium-layer (3-500 μm, HV 900-1100)Ni-P amorphous layer (3-30 μm, HV 1300)Surface hardening using inductive heating and subsequent rapid cooling
Inductor
Cog wheel
Inductor
Cog wheel
forrás: Szurdán Szabolcs
Deposition of thin layers by physical methods (Physical Vapour
Deposition, PVD)
• favour:
• High melting point metals can be deposited to low substrat temperature because• T substrat can be low
• The electrical conductivity of substrate not necessary
• Complex multilayers can be deposited
• Alloy deposition is also possible
• „clean technology” (without the formation of products causing environmental pollution)
• limits:
• Expensive (vacuum circumstances)
PVD (physical vapor deposition)The original, traditional technologies: chemical reactions are not included ( i.e. mirror production)
Schematic illustration of the principle
The technical arrangementCrucial in every deposition is the layer duration, which is influenced mainly by the surface preparation
(cleaning)
Heating
Substrate
Source
Vacuum system
Source
Chamber
Window
Layer thickness measure
Substrate holder
Evaporate source
Cover plate
Freezer
Diffusion pump
Pre-vacuum pumps
Valve
Mask
Physical Vapour Deposition
Source: Platit
0,1
Ts/Tm
0,60,50,40,30,2 0,7
The real structure of the deposited layer versus the substrat to melting point temperature
Deposition of TiN layer on the surface of tools for the purpose of surface hardenening
The dimensions
Source: Platit
Some another exmples
Source: Platit
The machined length versus the main machining parameters: cutting speed (a) and feed (b) ( • TiN coated, o TiN coated and newly grinded, □nitride coating ■ without coating
Mac
hin
ed l
eng
th [
m]
Mac
hin
ed l
eng
th [
m]
Cutting speed [m/min] Feed [mm/rev]
Chemical Vapour Deposition, (CVD)basic principles
In the original form, the procedure consist of two isothermal reactions:a.) at T1 temperature M +nXMXn (M layer forming metal , X halogen) At T1 a volatile compound is formedb.) at T2 (T2 > T1 ) MXnM + nX Thermal decomposition of MXn occur on the substrate surface Subsequently the decomposition process, the halogen molecule is circuated (in order to form new volatile molecules)
Typical chemical reactions in the CVD procedure: Metal-halogenides are often used as precursor materials in these techniques.The reason: volatile compounds (high tension even at low temperatures!) (see tables)
Besides the metal-layer depositions, the method also used for compound depositions (refractory carbides, silicides, borides)
Typical CVD reactions
CrI2(g) 800-1000 ºC Cr(s) + 2I(g)
WF6(g) + 3H2(g) 350-1000ºC W(s) + 6HF(g)
WCl6(g) + 3H2(g) 500-1100ºC W(s) + 6HCl(g)
TaCl5(g) +5/2 H2(g)700-1100ºC Ta(s) + 5HCl(g)
(C8H10)2Cr(g)400-600ºC a Cr(s) + 2C8H10(g)
Ni(CO)4 150-200ºC b Ni(s) + 4CO (g)
Al2Cl6(g) + 3H2O(g) 800-1400ºC Al2O3(s) + 6HCl(g)
BCl3(g) + NH3(g) 500-1500ºC BN(s) + 3HCl(g)
TiCl4(g) + CH4(g) 800-1100ºC TiC(s)+ 4HCl(g)
Ga(g) + AsCl3(g) + 3/2H2(g) 750-900ºC GaAs(s) + 3HCl(g)
Typical reactants, processing parameters for a few depositions
Typical reactants, processing
parameters for a few depositions
layer reactant Add. reactant
T (C) pressure(kPa)
Deposition velocity(nm/min)
W WF6
WCl6
WCl6
W(CO)6
H2
H2
------
250-1200850-14001400-2000180-600
0,133-1000,133-2,670,133-2,670,013-0,133
0,127-50,80,254-38,12,54-50,80,127-1,27
Mo MoF6
MoCl5
MoCl5
Mo(CO)6
H2
H2
------
700-1200650-12001250-1600150-600
2,67-46,70,133-2,671,33-2670,013-0,133
1,27-30,51,27-20,32,54-17,80,127-1,27
Re ReF6
ReCl5
NbCl5
NbCl5
NbBr5
H2
---H2
---H2
400-1400800-1200800-12001880800-1200
0,133-13,30,133-26,70,133-1000,133-2,670,133-100
1,27-15,21,27-15,20,076-25,42,540,076-25,4
Nb NbCl5
NbCl5
NbBr5
H2
---H2
800-12001880800-1200
0,133-1000,133-2,670,133-100
0,076-25,42,540,076-25,4
Ta TaCl5
TaCl5
H2
---
800-12002000
0,133-1000,133-2,67
0,076-25,42,54
Zr ZrI4 --- 1200-1600 0,133-2,67 1,27-2,54
Hf HfI4 --- 1400-2000 0,133-2,67 1,27-2,54
Ni Ni(CO)4 --- 150-250 13,3-100 2,54-38,1
Fe Fe(CO)5 --- 150-450 13,3-100 2,54-50,8
V VI2 --- 1000-1200 0,133-2,67 1,27-2,54
Cr CrI3 --- 1000-1200 0,133-2,67 1,27-2,54
Ti TiI4 --- 1000-1400 0,133-2,67 1,27-2,54
The important metals and ceramics produced by the CVD method
Metals Cu, Be, Al, Ti, Zr, Hf, Th, Ge, Sn, Pb, V, Nb, Ta, As, Sb, Bi, Cr, Mo, W, U, Re, Fe, Co, Ni, Ru, Rh, Os, Ir, Pt
Graphite carbides karbon C, B4C, SiC, TiC, ZrC, HfC, ThC, ThC2,VC,
NbC, Nb2C, TaC, Ta2C, CrC, Cr4C, Cr7C3,
Cr3C2, MoC, Mo2C, WC, W2C, VC2, V2C3
Nitrides BN, TiN, ZrN, VN, NbN, TaN, Si3N4
Boron and borides B, AlB2, TiB2, ZrB2, ThB4, ThB, NbB, TaB,
MoB, Mo3B2, WB, Fr2B, FeB, NiB, Ni3B2,
Ni2B
Silicon and silicides Si és Ti, Zr, Nb, Mo, W, Mn, Fe, Ni, Co and varies silicides
Oxides Al2O3, BeO, SiO2, ZrO2, Cr2O3, SnO2
Examples for the compound-layer deposition
• The TiN layer deposition:
• 2 TiCl4 +4 H2 +N2 2 TiN +8HCl
• Al2O3 layer deposition:
• 2AlCl3 +3CO2 +H2 Al2O3 +3CO +6HCl
The scheme of complete unit for CVD technology
Gases
Halide preparatory
Gas mixer
Programming unit
Deposition chambers
Outgoing gas cleaner and neutralizer
Heating bell
Vacuum pump
Hea
tin
g
con
tro
ller
Heating bell
Gas
su
pp
ly
The properties of deposits produced by CVD ,
layer-substrate: the compatibility
Favour: -high temperature: deposit accomodat even the complicated,
irregular surfaces (inner surfaces can be covered)
Another example
Tantállal bevont gégecső
The limits:
• The high substrat temperature (for example for structural or carbon steels is not recommended! 6-800 oC!)
• Expensive reactants
The properties of CVD-produced policrystalline diamond layers:
high chemical resistance, high hardness, high wear resistance, low frictional resistance
Polymer
Diamond
DLC
Graphite
Gyémánt és gyémántszerű amorf rétegek
DLC: Diamond-Like Carbon
Hardness and young moduli of carbon- based coated layers
Me: fém az elektromos vezetőképesség növeléséhez, fém-karbidokH: hidrogéntartalom a C2H2 elbomlásából a: amorf fázis tartalmú rétegSi: szilíciumtartalomi-C: mátrix sp3-as kötésekkel, de amorf
The techniques of plasma spraying
Helium
Hővezetési tényező
Plazmagáz energiatartalma
Shematic drawing of plasma spraying and the SEM photograph of the sprayed coating
Characteristics of plasma-sprayed layers
Improvement of
Succesfully applied for
•Abrasive properties•Hardness•Corrosion resistance•(Especially in those cases, when the base material is low-cost
•improvement of bio-compatibility (implanted parts)
•the surface improvement of carbon-steels
•surface hardness increase •corrosion resistance increase
The modes of plasma welding:inner, outher wire supply, powder supply
The laser surface treatments
The effectivity highly depends on the absorption degree
The absorption degree of various laser beams as a function of wavelengths
Exc
imer
lase
r
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.1 1 10 100Hullámhossz [m]
Ab
szo
rpci
ós
fok
[%
]
Exc
imer
léz
er
Acél
Fe
Mo
Al
Cu
Au
AgN
d:Y
AG
léz
er
CO
2 l
ézer
Dió
da
léz
er
30
20
10
Iron
Wavelength (m)
Ab
so
rpti
on
de
gre
e [
%]
Nd:
:YaG
lase
r
Dio
de la
ser
Exc
imer
lase
r
CO
2 la
ser
The thickness of hardened layer as a function scanning rate on steels with various surface roughness
The absorption degree also depends on the surface roughness
0.4
0.8
1.2
1.6
400 500 600 700
előtolási sebesség [mm/min]
edze
tt r
éteg
vas
tags
ága
[mm
]
mart felület
köszörült felületpolírozott felület
Anyag: CMo4P= 2000 W
Milled surface
Grinded surface
Polished surface
Material: CMo4
Feed [mm/min]
Har
den
ed l
ayer
th
icjn
ess
[mm
]
Laser marking on steel surfaces
The local structural change as the basis of code formation
Depending on the applied energy density various structural changes can be induced
(phase transformation, recrystallisation etc)