Task 6.1 Material for heat transfer components for heavy liquid metal reactors – KIT contribution

IHM/ KIT/ Campus Nord 1 | Alfons Weisenburger| LEADER Bologna November 17th , 2010

Task 6.1 Material for heat transfer components for heavy liquid metal reactors (KIT-18, ENEA-3, UJV-7) Month 1 – 36

• Determine important mechanical properties of T91 with and without surface protection like creep and stress in combination with Pb of materials for heat transfer components• Transfer the surface protection process (GESA) to steam generator geometry• Determine the heat transfer properties of materials in contact with Pb• Assess the possibility to aluminize the entire reactor core internals inclusive pressure vessel - specific request from Design

Task responsible persons:KIT: Alfons Weisenburger; ENEA: Alessandro Gessi; UJV: Anna Hojna

Deliverables:D33 – Summary of HLM reactors materials (M36) –KITTechnical reports: T09 - Heat transfer properties (M24) – KIT T13 - Surface aluminizing of steam generator components (M30) – KITT17 - Influence of lead on mechanical properties (M36) – KIT-G, ENEA, UJV


Task 6.1 Material for heat transfer components for heavy liquid metal reactors – KIT contribution

Surface aluminizing – GESA process

• Based on ELSY and DEMETRA surface treatment procedure using GESA will be optimized for cladding tubes:

Operating GESA IV – cylindrical cathode - optimization

Optimizing coating composition – (GETMAT – own R&D)

• Transfer of surface aluminizing method to steam generator geometries. Tubes for steam generators with different bending radius shall be tested under different loads in lead environment. The creep and stress shall be measured in situ using high temperature strain gauges.

Stress dependent significant influence of LBE on creep to rupture at 550 °C detected

• Identification of threshold stresses of creep to rupture tests, below which the influence of the lead on the mechanical properties is negligible. Especially the stress limits for surface alloyed specimens will be addressed in this task.

Thermal conductivity, Heat transfer of oxidized T91 in Pb is still discussed:

• Dedicated tests to measure the thermal conductivity and/or thermal diffusivity of oxidized steel surfaces with adherent lead will be performed.

Assess the possibility to aluminize the entire reactor core internals inclusive pressure vessel - specific request from Design

• Looking for different aluminizing processes suitable for large components

KIT will participate to all Technical reports and the Deliverable


Surface modification using Pulsed Electron Beams (GESA)(Process development in cooperation with NIIEFA, St. Petersburg)

Volumetric Heating:rate: < 109 K/stime: < 40 µs

Melt layer:depth: < 100 µmcooling: < 107 K/s(heat conduction)

Surface alloyed layer

e--beam

Magnetic-coil

Anode

Target

GESA facility

Electron beam Parameter:

Electron Energy:125 keV

Power density : 2 MW/cm²Pulse durationcontrollable: < 40 µsBeam diameter: ~ 4cm GESA ITreatable length ~ 30 cm GESA IV

LPPS sprayedFeCrAl layer

T91

Substrate temperature remains relatively low – no micro-structural changes in T91 observed

cathode


Al content ~ 5 - 7 wt%

Al content ~ 10 wt%

T91 + FeCrAlY layer before and after surface modification

As sprayed

After GESA treatment

0 10 20 30 400

10

20

30

40

50

60

70

80

90

100

Fe,

Cr,

Al c

onte

nt in

%

distance from surface in m

Fe Cr Al

0 5 10 15 20 250

10

20

30

40

50

60

70

80

90

100

Fe,

Cr,

Al c

ontn

et in

%

distance from surface

Fe Cr Al

Surface smoothed, Pores are removed, layer densified, metallic bonding to substrate



different powder compositions were selected:

Al12Cr14, Al7Cr14 – 1000h test’s in COSTA at 550°C and 650°C available•GESA treated Al12Cr14 FeCrAlY form in LBE - if coating quality is suitable - at 550 and 650 °C protective Al2O3 scalesAl content after GESA 6 – 9 wt%

GESA treated Al7Cr14 do not form generally at 550 and 650 °C protective Al2O3 scales - Al content after GESA < 4 wt% Three “new” coatings Al12Cr14, Al12Cr9, Al12Cr14 Y-free – GESA treated – Al content after GESA ~ 5-10 wt%

Recently started – start of exposure new coatings in Pb at 450, 500, 550°C and respective Gas-atmosphere – short term quality proof test

Al12Cr14 FeCrAlY after 1000h in LBE at 550°C

Operating GESA IV – cylindrical cathode – optimization - ongoing R&D• measurement of beam homogeneity• Applying Pre-pulse to clean surface of cladding tube




Transfer of surface aluminizing method to steam generator geometries.

Tubes for steam generators with different bending radius shall be tested under different loads in lead environment. The creep and stress shall be measured in situ using high temperature strain gauges.

Can surface aluminized material be bended – what is limiting radius?

Status: First bending test’s of GESA modified FeCrAlY coated T91 (Y. Dai PSI)

7%16%

7%

Up to 16% deformation no cracks – no delamination – surface graded material


Future steps:

FeCrAlY coating to be applied on SG tube sections – bended and not bended – before March 2011

GESA (GESAIV) - treatment of such tubes –should be due to larger diameter easier compared with cladding tubes(Bended tube sections can not be treated using GESA IV)

Evaluation of max. bending radius after GESA treatment – flat specimens with miniaturized 3point bending test for SEM

Test of bended specimens under load in Pb at 500 to 600°C with in-situ stress and strain measurement

Influence of bending radius in stability of FeCrAlY surface aluminized T91

part of a

Master thesis officially starting in March 2011 until August 2011



Identification of threshold stresses of creep to rupture tests, below which the influence of the lead on the mechanical properties is negligible. Especially the stress limits for surface alloyed specimens will be addressed in this task.


Influence of PbBi on time to rupture of T91 orig at 550°C

Significant reduction in time to rupture of T91 due to contact with PbBi

Oxide scale cracks PbBi penetrates and reduces the surface energy – Rebinder effect – stress corrosion cracking


Comparison of secondary creep rates of T91 in air and PbBi at 550 °C

Stress [MPa]

Ratio of 2nd creep rates,

LBE/air

140 27

160 35

180 44

200 53

Influence of PbBi

Creep rate in PbBi up to 50 times higher than in air

Ratio of creep rate in PbBi and air is stress dependant

At low stresses – no cracking of oxide scale ?? – no direct contact with PbBi – no influence on creep strength - threshold stress ??


Creep tests at low stresses at 550°C – Threshold stress ??

0 200 400 600 800 1000 1200 1400 16000,0

0,2

0,4

0,6

0,8

1,0

1,2

1,4

60 MPa - PbBi 80 MPa - PbBi 100 MPa - PbBi 120 MPa - PbBi 140 MPa - Luft 140 MPa - PbBi

stra

in in

%

Duration in hour's

60 to 120 MPa no change - as long as oxide scale intact no influence cracks at 60 and 80 MPa reduction in strength

Any deterioration of the oxide scale results in reduced creep strength

60Mpa

CracksPbBi can penetrate

120 MPa

No cracksNo PbBi No influence


Stress: 200 and 220 MPa

0 500 1000 1500 2000 25000,0

0,5

1,0

1,5

2,0

2,5

3,0

3,5

4,0

4,5

5,0

160 MPa 180 MPa

T91 orig air GESA inPbBi

Str

ain

in %

Time in h

160 MPa 180 MPa

Stress 160 and 180 MPa

Comparison of creep of GESA surface modified T91 in PbBi and T91 orig. in air at 550°C

0 500 1000 1500 2000 2500 3000 3500 4000 4500 50000

2

4

6

8

10

12

14

16

18

20

22

200 MPa 220 MPa

stra

in in

%

time in h

200 MPa 220 MPa

T91 orig air GESA inPbBi

T91 with GESA modified FeCrAl layer also shows an influence of LBE. However, this deterioration is significantly reduced compared to the T91 original.At 200MPa still a reduction in time to rupture from 3500 auf 2500h is observed. At a strain of about 3.5% influence of PbBi becomes visible.


Creep to rupture of T91 with and without GESA in PbBi and air at 550°C

Oxide scale cracks PbBi penetrates the crack PbBi reduces surface energy of steel dissolutes steel elements and penetrates the grain boundaries crack propagation

Stress over time to rupture of T91 original and T91 GESA

GESA modified FeCrAlY layer reduces the negative influence of PbBiNo cracking of oxide scale no influence of PbBi

10 100 1000 10000

100

150

200

250

300

GESA 600 PbBi GESA 600 Air T91 orig 600 air (spire)

GESA 550 PbBi GESA 550 Air T91 orig Luft (spire)

T91 orig 550 PbBi

Str

ess

(MP

a)

time to rupture (h)



Identification of threshold stresses of creep to rupture tests, below which the influence of the lead on the mechanical properties is negligible. Especially the stress limits for surface alloyed specimens will be addressed in this task.

Status and planned tests:

Creep to rupture tests in Pb at 550°C at stress levels of 100, 120, 140, 180, 200 MPa

Specimens: T91, T91 surface alloyed with GESA

Schedule: Preparation of specimens: March 2011 Coating deposition: August 2011

GESA treatment : October 2011 Creep to rupture tests: October 2012


Involvement of UJV In Task 6.1

• Within the Task 6.1, the UJV Rez plc plan to perform– T91 steel will be exposed in convectional loop COLONRI II in liquid lead

environment of 550-650˚C. Then same samples will be mechanically tested in air and liquid lead and post test examined.

• Machine samples - tensile bars• Pre-expositon in COLONRI II 550-650˚C liquid lead• SSRT tests at 350 – 450˚C in air and liquid lead• SEM• Report

Already shown at Kick – off meeting – no new information


Task 6.1 Material for heat transfer components for heavy liquid metal reactors – KIT contribution


• Based on ELSY and DEMETRA surface treatment procedure using GESA will be optimized for cladding tubes:

Operating GESA IV – cylindrical cathode - optimization


• Transfer of surface aluminizing method to steam generator geometries. Tubes for steam generators with different bending radius shall be tested under different loads in lead environment. The creep and stress shall be measured in situ using high temperature strain gauges.


• Identification of threshold stresses of creep to rupture tests, below which the influence of the lead on the mechanical properties is negligible. Especially the stress limits for surface alloyed specimens will be addressed in this task.

Thermal conductivity, Heat transfer of oxidized T91 in Pb is still discussed:

• Dedicated tests to measure the thermal conductivity and/or thermal diffusivity of oxidized steel surfaces with adherent lead will be performed.


• Looking for different aluminizing processes suitable for large components

KIT will participate to all Technical reports and the Deliverable


Heat transport properties

k : thermal conductivity [W/(mK)]thermal diffusivity [m^2/s]r : density [kg/m3]Cp : specific heat capacity [J/(kgK)]

k = Cp

The sample is mounted on a carrier system which is located in a furnace. After the sample reaches a predetermined temperature, a burst of energy emanating from a pulsed laser is absorbed on the front face of the sample, resulting in homogeneous heating. The relative temperature increase on the rear face of the sample is then measured as a function of time by an IR detector. The thermal diffusivity is computed by the software using these time/ relative temperature increase data. For adiabatic conditions, is determined by the equation: = 0,1388 l^2/t (l: sample thickness, t: time at 50% of the temperature increase)


Heat transport properties

Status:

Thermal diffusivity measurements were performed on disks made out of T91, Fe84Cr12Al4 alloy and T91+FeCrAlY+GESA

Future steps:

Exposure of specimens to oxygen containing Pb:

Temperature: 550°C times: 1000h’s and 3000h’s

Thermal diffusivity measurements on samples initially exposed to oxygen containing liquid Pb at different temperatures and for different periods: T91, 9Cr –ODS steel, T91+FeCrAlY+GESA, etc.

T09 – Heat transfer properties will be in time (March 2012)


Heat conduction as function of oxidescale thicknessin combination with heat transfer simulation

Pb

Pb at 500°C - Isolation is removed - Measurement area will be cooled – Cooling is stopped and warming up will be determined as function of time – repetition several times per month – influence of oxide scale thickness) – can be determined separately and at end of experimentInfrared camera records temperature development of steel surface

Infrared camera

Isolation

Test section

cooling

Pb

Temp. Measurement Pb

Isolation


Use of calorimeter to heat or cool the liquid metal with high accuracyMeasurement of liquid Pb temperature in front and after the calorimeterUsing heat transfer simulations to calculate the heat conduction

Pb

Isolation

Test section

Pb

Temp. Measurement in Pb

Isolation

2nd option use of calorimeter – actual preferred

calorimeter


TELEMAT at the KALLA-LabTest Loop for Lead Material Testing

Temperature up to 650 °C – 700°C possible

Pb-Inventory 150 l

DN 40 / DN 20 tubing

flexible test branch with

up to 2 m long test setup – can be used to address the „wrapper“ problem –direct flow impact – local turbulent flow pattern

EM Pump with 2 m³/h, resp. 2 m/s in

the test section

heater-recuperator-cooler-design

design for continuous operation

over several thousand hours

Schedule: Loop should be ready beginning of 2011Heat transfer measurements will be the 1st to be performedTemperature for this experiment 500 – 550°C


Pack Aluminide

The Aluminide Coating is applied by pack cementation to internal and external surfaces of Commercial Aero, Military Aero, Small Engines including APUs, and Aeroderivative/IGT compressor blades, disks and diaphragms and turbine blades, vanes, wheels and tip shoes.

Gas Phase Aluminide

The Aluminide Coating is applied by gas phase to internal and external surfaces of Commercial Aero, Military Aero, Small Engines including APUs, and Aeroderivative/IGT turbine blades, vanes, wheels and tip shoes.

Diffusion Coatings are applied for internal and external oxidation and corrosion protection.

Chromalloy


Very limited looking for different aluminizing processes suitable for large components Aluminization - Surface alloying of Al on Industrial level:


CVD Chemical vapor depositon


Ion Bond

Chemical Vapor Aluminizing (CVA) is based on the CVD process and is used for depositing CVD aluminide coatings for high temperature applications. The Bernex ATL CVA is an advanced technology that offers a more environmentally friendly, better forming alternative to older pack, out of pack and slurry technologies.Process TemperatureThe typical process temperature for the CVA process is between 900(°) C and 1050(°) C.Items Typically Coated The CVA process is used to protect parts operating in high temperature environments against corrosion and oxidation. As a result, the most common parts coated are high temperature industrial and aero gas turbine components, such as the hot section turbine blades. Coatings Typically Deposited The CVA process produces a highly controllable, extremely homogeneous aluminide diffusion layer. Unlike other aluminizing processes, the Bernex ATL process is suitable for coating the internal cooling channels of turbine blades.Advantages of the process:Clean process compared to pack and slurry techniquesThe process is precisely controlledIt is possible to coat internal cooling channelsThe coating is uniformly depositedLow surface defect density


Berolina Metallspritztechnik Wesnigk GmbHChromin Maastricht BVbero-arc alutherm – Arc spraying of pure aluminum –Heat treament to diffuse the Al into the substrate – ALUMINUM/ALONIZING - alitieren (german acronym)

Inserting aluminum or aluminum/chromium has special properties. This diffusion coating is especially used as an anti-diffusion coating in chemical and petrochemical industries. This coating can prevent diffusion of, among other things, carbon from appearing in pipes and cracking installations. The standard 3200 mm length treatment may possibly be extended on application.* This aluminum or aluminum/chromium coating is diffused into the metal surface by means of diffusion.* Process temperature 850-1050°C.* Diffusion thickness: 30-1000 microns. (duplex coating).* Anti-diffusion properties.* Heat-resistant up to 1100°C.* Corrosion and erosion resistant .* Applicable to all ferrous metals, nickel and cobalt.* Standard maximum dimensions: 3200x2000x850mm.


Summary:

All three methods are basically similar:Coating deposition plus subsequent heat treatmentTemperatures are for all processes relatively high – suitability for F/M steels like T91 is questionable but for 316 type steel off-course well suitable

Next steps:

Getting in contact with the different companies

to discuss the possibility to aluminize large scale components like reactor vessel


Task 6.2 Materials for mechanical pump for heavy liquid metal reactors (ENEA - 5, KIT - 5)Month 1 - 30

The erosion of structural materials in fluent lead is considered acceptable if the relative velocity between the lead and the structural surface is kept below 2 m/s. This limit cannot be respected for the mechanical pump where the relative velocity is up to 10 m/s or even higher at local areas.

Material capable to operate in fluent lead with relative velocity up to 10 m/s and environment temperature up to 500°C with acceptable performance shall be individuated and qualified. Specific materials (Maxthal, SiSiC) tests in representative conditions (speed, mechanical load, thermohydraulic conditions) for heavy liquid metal reactors will be performed.

Task responsible persons:ENEA: Mariano Tarantino; KIT: Adrian Jianu; Deliverables:D16 - Erosion stability of materials in fast flowing lead (M30) – ENEA, KIT


First test with specific conditions show severe erosion

•Promising pump materials (Maxthal, SiSiC, ….) will be tested under such conditions•Detailed modeling of flow conditions at specimens to understand the flow impact

KIT will contribute to Deliverable D16

Task 6.2 Materials for mechanical pump for heavy liquid metal reactors (ENEA, KIT-G) Month 1 - 30

Test performed with 2.5 m/s


Actual running tests

Temperature of Pb: 500°COxygen content: 10-6 wt%Speed of HLM: 2.5m/s – like in previous testIncreasing the speed will be investigatedHighly turbulent flow – Pb directed on the specimenNot only tangential action of the Pb Materials:SiSiC; Maxthal; FeCrAl GESA; Noriloy; Norihard

Test started Oct. 6th 2000h‘s – until end of DecemberFlow conditions will be modeled

Pb

Documents

Task 6.1 Material for heat transfer components for heavy liquid metal reactors – KIT contribution