Weld Cracking in a Cast Ni-based Superalloy

Weld Cracking in a Cast Ni-basedSuperalloy

Sukhdeep Singh1, Joel Andersson2

1. Department of Industrial and Materials Science, Chalmers University of Technology, Sweden

2. Department of Engineering Science, University West, Sweden

2

Hot Structural PartsShaft

Vanes

Fan/compressor structures

Turbine structures

Compressor rotorsCombustor structure

LPT-Case

Fan Case

Introduction

3

Composition in wt%

Ni Fe Cr Co Nb Mo Ti Al … Si B

Cast 282 Bal. 0.1 19.4 10.2 0.1 8.4 2.12 1.5 … 0.01 0.005

Cast 718 52.98 Bal. 18.11 0.07 5.30 2.98 0.99 0.42 … 0.07 0.03

Haynes® 282®

Alloy 718

Strengthening phase

γ´ (gamma prime)

γ´´ (double-prime)

Segregating phase

Mo-enriched

Nb-enriched

Cast Haynes® 282®

4

Heat Treatments

As Cast

1120°C/4h

1160°C/4h

1190°C/4h

1135°C/0.5h

Pseudo-HIP

5

Research Objective

How different heat treatments affect the HAZ liquation crackingsusceptibility of cast Haynes® 282® ?

6

Heat Treatments

1120°C/4h

1160°C/4h 1190°C/4h

As Cast

7

Heat Treatments

1120°C/4h

1190°C/4h

8

Parameters: Welding Speed = 1 mm/s

Stroke rate = 10 mm/s

Current = 70 A

Arc =2 mm

Ar gas flow = 15 l/min

Radii: 60,100,150 (mm)

Varestraint Testing

9

HAZ Cracking

1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8

0

1

2

3

4

5

Avg

.TC

L(m

m)

Augmented Strain (%)

As Cast

1120°C/4h

1160°C/4h

1190°C/4h

10

Avg.TCL

1190As Cast 1120-1160

As Cast 1120°C/4h 1160°C/4h 1190°C/4h

GS 1.6±0.4 1.5±0.2 1.6±0.3 1.6±0.2

HV 245±40 215±10 230±20 220±10

Vv% 1.5±0.2 0.9±0.1 0.7±0.1 0.5±0.1

HAZ Cracking

°C

11

Avg.TCL

1190As Cast 1120-1160

HAZ Cracking

°C

As Cast 1120°C/4h 1160°C/4h 1190°C/4h

GS 1.6±0.4 1.5±0.2 1.6±0.3 1.6±0.2

HV 245±40 215±10 230±20 220±10

Vv% 1.5±0.2 0.9±0.1 0.7±0.1 0.5±0.1

12

Avg.TCL

1190As Cast 1120-1160

HAZ Cracking

°C

As Cast 1120°C/4h 1160°C/4h 1190°C/4h

GS 1.6±0.4 1.5±0.2 1.6±0.3 1.6±0.2

HV 245±40 215±10 230±20 220±10

Vv% 1.5±0.2 0.9±0.1 0.7±0.1 0.5±0.1

13

Avg.TCL

1190As Cast 1120-1160

HAZ Cracking

°C

As Cast 1120°C/4h 1160°C/4h 1190°C/4h

GS 1.6±0.4 1.5±0.2 1.6±0.3 1.6±0.2

HV 245±40 215±10 230±20 220±10

Vv% 1.5±0.2 0.9±0.1 0.7±0.1 0.5±0.1

14

• Objective :

• Primary : recorded B distribution in grain boundaries, variations among heattreatments

• Secondary : Si and P imaging

• Conditions :

• 1120,1160,1190°C/4h

NanoSIMS Analysis

15

NanoSIMS analysis at 1120°C

C Si P

B

0.0 0.5 1.0 1.5 2.0

0

200

400

600

800

1000

1200

Inte

nsi

ty(C

ou

nts

)

Distance (µm)

11B12C2

3-4

Carbon Boron

16


C Si P

B

Carbon Boron

17


C Si

P B

0 1 2 3 4 5 6

15

20

25

30

35

40

Inte

nsity

(Cou

nts

)Distance (µm)

11B

0 1 2 3 4 5

15

20

25

30

35

40

45

50

Inte

nsi

ty(C

ou

nts

)

Distance (µm)

11B

0 1 2 3 4 5

15

20

25

30

35

40

45In

ten

sity

(Co

unts

)

Distance (µm)

11B

1-2 3-4

5-6

18

Hot Ductility - On Heating

Gleeble Parameters:

Heating rate

Peak temperature

Stroke rate

Holding time at peak temperature

Holding time at test temperature

111 °C/s

1200 °C

55 mm/s

0.03 s

0.03 s1050 1100 1150 1200 1250

0

10

20

30

40

50

60

70

80

90

W. 282 On-H.1120°C/4h1190°C/4h

Are

aR

ed

uct

ion

(%)

Temperature (ºC)

19

Hot Ductility - On heating at 1150°C

20


21

Summary

• Ranking according to Varestraint weldability study:• 1190°C/4h higher cracking• 1120-1160°C/4h lower cracking sensivity

• NanoSIMS analysis:• B is found only in compound at 1120° and 1160° together with C• B segregates at the grain boundaries at 1190°• Complete dissolution of C-B particles and the segregation at the grain

boundaries contributed to exacerbated HAZ cracking

22

Thank You!

23

• Occurs during cooling from hightemperature due to diffusion of vacancy-solutes to vacancy sinks

• Increases with increasing temperature

• Occurs when a material is held at hightemperature sufficiently long to permitappreciable diffusion of solute atomsfrom the matrix to the grain boundaries

• Decreases with increasing temperature

Equilibrium vs Non-Eq. Segregation

24

NanoSIMS analysis at As cast

25

NanoSIMS analysis at As Cast

C Si P

B

0 1 2 3 4

0

5

10

15

20

25

30

35

40

45

50

55

60

65

70

75

80

Inte

nsi

ty(C

ou

nts

)

Distance (µm)

11B

26


27


28

HAZ Cracking

HAZ FZ HAZ FZ

1120°C/4h 1190°C/4h

29


1120°C/4h

30

Mo-rich precipitates

As Cast 1120°C/4h 1160°C/4h 1190°C/4h

Vv Mo(%) 0.14±0.2 0.31±0.2 0.13±0.2 00±00

31

On-Heating/On-Cooling f(B)

Influence of B content on Hot Cracking sensivity of weld heat affected zone in Incoloy 800Saito et al., Transactions ISIJ, Vol. 27, 1987

1050 1100 1150 1200 1250

0

10

20

30

40

50

60

70

80 Wrought 282As Cast1120°C/4h1160°C/4h1190°C/4h

Are

aR

ed

uction

(%)

Temperature (ºC)

32

Hot Structural PartsShaft

Vanes

Fan/compressor structures

Turbine structures

Compressor rotorsCombustor structure

LPT-Case

Fan Case

Introduction

33

Heat Treatments

1120°C/4h

1160°C/4h

1190°C/4h

As Cast

0.9±0.1

0.7±0.1

0.5±0.1

1.5±0.2

1.5±0.2

1.6±0.3

1.6±0.2

1.6±0.4

215±10

230±20

220±10

245±40

Vv% GS HV

34

Heat Treatments

1120°C/4h

1160°C/4h

1190°C/4h

As Cast

0.9±0.1

0.7±0.1

0.5±0.1

1.5±0.2

0.31±0.2

0.13±0.2

00±00

0.14±0.2

1.5±0.2

1.6±0.3

1.6±0.2

1.6±0.4

215±10

230±20

220±10

245±40

Vv% Vv Mo% GS HV

35

Avg.TCL

1190As Cast 1120-1160

HAZ Cracking

Boron

Enrichment factor: grain size, starting temperature, coolingrate…

Karlsson, Non-equilibrium grain boundary segregation of B in austenitic stainless steel_III.Computer simulations, Acta metall. Vol. 36, 1988

Enrichment factor: grain size, starting temperature, coolingrate…


Peak Temp.: NDT+50

0.01 B0.002 B

West, S.L. Phd Thesis, A study of weld heat-affected zone liquation in cast nickel-base superalloys,The Ohio State University, 1991.

39

Stress relaxation through liquid

TCL

Liquid film thickness

σ = 2γSL/h

1120

1190

As Cast ??

(50nmresolution)

Moveable

Primary Ions (PI)

Secondary Ions (SI)

SampleSurface

SIMS NanoSIMS

41

Outline

• Introduction

• Experimental

• Results & Discussion

• Summary

• Future Work

42

It is function of:• Heat treatment temperature• Cooling rate• Concentration of solute atoms• Binding energy between solute atoms and vacancies


Non-equilibrium segregation

43

• High tendency of B to segregate at the grain boundary vacancies• Surface active element affecting the grain boundary wettability

Varestraint Testing

• Cracking increases • Reduces the NDT and NST• BTR increases

Gleeble Testing

Effect of B on weldability

44

• SETTINGS :

• Implantation 1017Cs+.cm-2 with D11 and ~ 180pA

• ES4 AS3 EnSopen, mass resolving power is put at ~10000

• mass table for (11B-), 11B12C-, 12C-, (12C2-), 28Si-, 31P-, 11B16O2-

• Current measurement ~ 1pA with D12,

• SAMPLES :

• As Cast, 1120,1160,1190°C/4h

• Objective :

• Primary : recorded B distribution in grain boundaries, variations among heattreatment

• Secondary : Si and P imaging

NanoSIMS for B analysis

Weld Cracking in a Cast Ni-based Superalloy

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