compositional and structural factors that influence hydrogen … · 2018-06-18 · ferrous physical...

Compositional and Structural Factors that Influence Hydrogen Induced Cracking and Hydrogen

Flaking in Steels

Allan Arenas and Shuai Cai Advisor: C. Isaac Garcia

Ferrous Physical Metallurgy Group MEMS Department

Image Quality or Inverse Lattice Distortion

LTP

HTP

Acknowledgements

To all the members of the Ingot Metallurgy Forum for their support and participation to make this program possible. The expected benefits of this program are to provide a Road-Map to increase the understanding and to control the metallurgical factors responsible for Hydrogen delayed failures (HDF) and Hydrogen induced cracking (HIC) in high alloyed steels. This program will also provide the education and training of graduate and undergraduate students interested in ferrous physical metallurgy.

• Objective • Background • Experimental Procedure

o Chemical Composition o Processing Information of As-received samples o Sample Preparation o Microstructural Analysis

• Results to Date • Discussion • Future Work

Content

Relevance to Goals and Objectives This research effort directly targets the following technology areas: • Assessment of alloy design, processing and solute

segregation. • Microstructural description and quantification. • Stereology and chemical description of non-metallic

inclusions and precipitates. • Transformation behavior, continuous cooling and/or

isothermal transformation. • Better understanding to reduce or eliminate hydrogen

embrittlement in large forgings.

Hydrogen Induced Cracking and Hydrogen Delayed Cracking

The exact mechanism of hydrogen embrittlement is “not well-known”. The initial step is the same: penetration of atomic hydrogen into the metal structure. Most of the mechanisms that have been proposed for hydrogen embrittlement are based on dislocation slip interference by dissolved hydrogen. This slip interference may be due to accumulation of hydrogen near dislocation sites, micro-voids, non-metallic inclusions, retained austenite and low temperature transformation products.

HE Domain

Environment Mechanical and Electrochemical

Effects

Materials

Hydrogen Induced Cracking (HIC) Susceptibility to HIC • P, S, Ni and Mn concentration – segregation and/or

promote retained austenite during transformation. • Slab/Ingot Reheating Temperature- Austenite grain

size. Grain boundary segregation- hardenability • Thermal Path (CCT or ITT) – decomposition of

austenite & transformation products. • Additional tempering treatments – softening,

precipitation hardening, retained austenite decomposition.

Proposed Program

Year 1 Year 1

Year 2

Study the Effect of TMP and Thermal Path on Transformation during CCT & ITT

F-start P-final

P-start

B-start B-final

YEAR 2

Experimental Procedure

NDE/NDT – Microstructural Analysis

Two different steel grades has been selected for this study. Since the start of the project 3 companies have provided samples. These samples have different shapes, process parameters and small variations on chemical composition. The ID of the companies has been designated as A, B and C according to the sample reception date.

Process Parameters

Company Grade Sample Forged Process Condition

A 4340 1 Yes Normalizing – Austenizing - Oil Quench - Temper

A 4340 AC No As Cast

A 8630 1 Yes Normalizing – Austenizing - Oil Quench - Temper

A 8630 AC No As Cast

B 4340 05-03 Yes Ingot – Soaking – Forging – Air Cooling

B 4340 05-02 Yes Ingot – Soaking – Forging – Air Cooling

B 8630 All of them.

Yes Ingot – Soaking – Forging – Air Cooling

C No Information is available

Chemical Composition (wt%)

Element Company A

4340 S1

Company A 4340 AC

Company B 4340 05

Company B 4340 87

Company A 8630 S1

Company A 8630 AC

Company B 8630 99

C 0.42 0.42 0.42 0.41 0.30 0.32 0.3

Mn 0.78 0.76 0.78 0.78 0.96 0.94 0.89

P 0.010 0.009 0.007 0.009 0.008 0.010 0.009

S 0.017 0.014 0.002 0.018 0.01 0.006 0.008

Si 0.29 0.32 0.28 0.34 0.35 0.30 0.32

Ni 1.72 1.74 0.86 1.67 0.85 0.85 0.44

Cr 0.90 0.86 0.86 0.86 1.10 0.99 0.47

Mo 0.29 0.26 0.29 0.22 0.48 0.43 0.16

V 0.052 0.006 0.005 0.006 0.008 0.007 0.002

Al 0.020 0.03 0.028 0.028 0.020 0.026 0.03

Cu 0.19 0.19 0.18 0.17 0.19 0.17 0.16

H 1.6ppm - - - 1 ppm -

HIC in welding

- Cold cracking/ HAZ cracking Source for hydrogen entrapment -Moisture -Organic compounds - Occurs 72 hrs. after welding - At 450 F hydrogen diffuses at rate of 1

inch /hr. - At 220 F - 1 inch / 48hr - At RT 1 inch /2 weeks

Hydrogen blistering

- Nucleation of hydrogen at internal defects - Rupture of material

Sulfide Stress Cracking

- If hydrogen sulfide is present will cause entry of hydrogen into the component (i.e. Sour service environment)

Examples of HIC manifestation

HIC HIC

EDS Analysis of undissolved FeNb paticles

The use of UT for flaw detection is not new and has been used for years as a quality control method. Between the most common aplications of UT systems is possible found the inspection of raw materials, casting, and forgings, engineering metals, composites, ceramics, and polymers, Carbon/Carbon composites, Carbon/Epoxy composites, Graphite-epoxy sandwich panels, Automotive clutch facings, Automobile brake pads, Asphalt concrete, Weldments, adhesive bonds, pipe, etc..

UT Immersion Tank

UT techniques have been used primary for defect detection but another major application is to help in the understanding and characterization of microstructures, grain sizes, etc.

A-scan

Flaw zone

Safe zone

Clean sample Sample with indication

C-scan

The different UT techniques mesure how a wave sound travels in a material. Changes in the material macro and microstructure generates changes in the wave sound propagation. These changes indicated that something is interfering with the sound wave propagation in the material. The level of absorption of the sound wave depends on the nature of the interfering factor. Our main interest is to identify the location of these changes generated by microstructural differences.

Special chemical etchants used in this study:

Etchant Composition Result

Nital 100 ml ethanol 99%, 10 ml nitric acid 65% General microstructure

LePera 50 ml Na2S2O5 1% in aqueous dilution, 50 ml picric acid 4% in ethanol

Retained austenite in White, Bainite in Brown

Beraha 50 ml Na2S2O5 1% in aqueous dilution, 50 ml picric acid 4% in ethanol

Colouring over the non ferritic structures

Kalling 33 ml destilled water, 33 ml ethanol 99%, 33 ml hydrochloric acid 32%, 1,5 g copper(II)-chloride

Grain boundaries, general structure

Nital + Sodium metabisulfate

Pre-etching with Nital, wet etching with Na2S2O5 10% in aqueous dilution

Different tonalities between non ferritic structures

DIC

Special etchants

SEM

EBSD - IPF

Using different metallographic techniques is possible to analyze the microstructure and the Hydrogen effect on these.

M-A

M-A

AHSA steel stained in boiling alkaline

chromate solution

New F α'

Old F

New F

α'

Old F

20mm

NDT/NDE was used as a tool to aid in the location of possible “indications – microstructural variations” before the microstructural characterization.

h= 129.42mm (5.09 in)

L= 105.75mm (4.13in)

W= 104.8mm (4.12in)

h

L

W

h= 130.01mm (5.11in)

L= 105.45mm (4.12in)

W= 104.3mm (4.13in)

h

L

W

4340

8630

h

h

L

W

W

L

l

l

h= 30mm (1.18 in)

L= 372.2mm (14.64in) l= 354mm (13.9in)

W= 97.3mm (3.83in)

108-03

AM988

h= 34mm (1.33 in)

L= 280.4mm (11in) l= 264mm (10.4in)

W= 78.5mm (3.09in)

COMPANY A

xx499-1-02

xx499-3-02

xx499-4-02

h= 40mm (1.57 in)

L= 149.67mm (5.9in)

W= 149.6mm (5.9in)

L

h

W

h= 51.7mm (2.03 in)

L= 148.92mm (5.9in)

W= 147.6mm (5.9in)

h= 66.7mm (2.62 in)

L= 150.1mm (5.9in)

W= 149.7mm (5.9in)

L

h

W

L

h

W

COMPANY B

xx405-1-03

h= 55mm (2.16 in)

D= 246mm ( 9.68in)

xx405-1-02

h D

h D h= 58mm (2.28in)

D= 244mm ( 2.60in)

D

h h= 46mm (1.81 in)

D= 207mm (8.15in )

xx487-1-02

h

L W

h

L

W

h= 6in L= 9in W= 5in

COMPANY C xxx201L

xxx172LL

h= 0.75in L= 9in W= 5in

The scan was performed using a bidirectional scanning where the acquired data is taken each 0.2mm. 1, 5 and 10Mhz transducers were used for the characterization. Z distance (the distance from the sample surface to the transducers) vary according to the sample thickness. Z distance was the same for all the used transducers (minor gate adjusting is needed) in order to keep the scanning conditions uniform. The samples were scanned trough the thickness ( h dimension according the sample drawings).

Scanning Direction

Z distance

Using the different transducers is possible see that using the 1 Mhz transducer is possible obtain more contrast between the lectures. This is the 8630 Company B J2499- 3-02 sample. Scanning parameters were the same for all the transducers. The sample orientation was also the same. Due this higher response in the 1Mhz transducer the following results correspond to 1Mhz signals.

20mm 1 Mhz

20mm 5 Mhz

20mm 10 Mhz

Sample Sectioning surface preparation

Macroetching

Sectioning Faces preparation Mounting

Results

Sample Gate size was selected to analyze 10mm sections looking for variations in the signals for 4340 Company A sample

Surface 10mm 20mm

30mm 40mm 50mm

60mm 70mm 80mm 90mm

100mm 110mm Bottom

Colors means the differences in the acquired waves. Homogeneous material would show a single color with different saturations. Different colors means significant signal responses.

10mm 10mm

50mm

29.4HRC

31.8HRC

29.4 HRC

31.8 HRC

Company A- 4340 Microstructures

-35

-30

-25

-20

-15

-10

-5

0

0 20 40 60 80 100 120 140

110mm

10mm

110mm

Pea

k A

mp d

B

31.8HRC

Depth mm

50mm

31.8 HRC

Company A- 4340 Microstructures

Sample Gate size was selected to analyze 5mm sections looking for variations in the signals for 4340 Company B sample

Surface 5mm 10mm

15mm 20mm 25mm

30mm 35mm 40mm

Bottom Colors means the differences in the acquired waves. Homogeneous material would show a single color with different saturations. Different colors means significant signal responses.

5mm

22.7HRC 32.9HRC

32.9 HRC

22.7 HRC

Company B 4340 Microstructures

25mm

20mm

32.9HRC

31.7HRC

32.9HRC

31.7HRC

-18

-15

-12

-9

-6

-3

0

0 10 20 30 40 50

35mm

32.8HRC

Pea

k A

mp d

B

Depth mm

5mm Edge

5mm Core

20mm

25mm

35mm

32.8 HRC

Sample Gate size was selected to analyze 10mm sections looking for variations in the signals for 4340 Company B disc sample

Surface 10mm 20mm

20mm

Bottom

30mm 40mm 50mm

Colors means the differences in the acquired waves. Homogeneous material would show a single color with different saturations. Different colors means significant signal responses.

10mm

20mm

30.3HRC

31.0HRC

30.3 HRC

31.0 HRC

-25

-20

-15

-10

-5

0

0 10 20 30 40 50 60

Depth mm

50mm

31.4HRC

Pea

k A

mp d

B

20mm

10mm

50mm

31.4 HRC

-35

-30

-25

-20

-15

-10

-5

0

0 20 40 60 80 100 120 140

Pea

k A

mp d

B 50mm

100mm 10mm

10mm

110mm

50mm

100mm

-25

-20

-15

-10

-5

0

0 10 20 30 40 50 60

Depth mm

J2487-1-02 Core J2487-1-02 J2405-1-02

-11.2 dB 20mm J2487-1-02 -13.97dB 35mm J2487-1-02 -13.34 dB20mm J2405-1-02

22.7HRC

32.9HRC

32.9HRC 31.7HRC

32.8HRC

30.3HRC

31.0HRC

31.4HRC

31.8HRC

29.4HRC 29.3HRC

4340 company A

-15.0 dB 10mm Company A

Depth mm

Pea

k A

mp d

B

Signal response Peak Amplitude and Hardness between the 4340 samples

Signal response Peak Amplitude and Hardness between the company A samples

-32

-27

-22

-17

-12

-7P

eak

Am

p d

B

10mm

10mm

50mm 110mm

50mm

100mm

8630 4340

* Same scanning parameters were used for both samples.

31.8HRC

29.4HRC 29.3HRC

27.6HRC

26.7HRC

27.3HRC

The microstructures generated by 8630 steel seems to produce lower signal attenuation than the microstructures generated by 4340 steel. Company A samples where used for this analysis cause have similar process and shape between them.

0

10

20

30

40

50

60

70

-35 -30 -25 -20 -15 -10 -5 0Peak Amp dB

Har

dn

ess

HR

C

Ferrite

Pearlite – Lamellar structure

Possible M-A Pro eutectoide

cementite

Signal response Peak Amplitude, Hardness Microstructure.

The microstructures corresponding to company B samples from 4340 and 8630. For both grades the Pearlitic structures are very close in their response even when chemical composition is different.

Microstructural Analysis OM and SEM results

xx499-1-02 Company B 8630 Microstructures

Inclusion Size Avg: 52microns

2% Nital

Le Pera

SEM

No Etching

262.7HV

Inclusion Size Avg: 49.7microns

2% Nital

Le Pera

SEM

No Etching


Sample 8630

Inclusion Size Avg: 42.11 microns

2% Nital

Le Pera

SEM

No Etching


Element % Wt

Mn 47.42

S 27.51

Fe 15.16 *

Others 9.91*

8630 Company B Inclusions Chemical Composition

Element % Wt

Mn 0.05

S 2.01

Fe 19.46 *

Si 70.42

Others 8.02

Element % Wt

Mn 47.42

S 27.51

Fe 15.16 *

Others 9.91*

8630 Company B Inclusions Chemical Composition

Company B Micro Hardness According Present Microstructures

XX405-1-02 (4340) Micro Hardness

XX499-3-02 (8630) Micro Hardness

XX405-1-02 (4340) Microstructure

8630 Microstructure

Summary (6 months progress report)

Note: No all the samples were received in May.

Step A 8630 A 4340 B4340 1 B4340 2 B 4340 3 B 8630 1 B 8630 2 B 8630 3 C 1 C 2

UT 1Mhz Scan DONE DONE DONE DONE DONE DONE DONE DONE DONE PENDING



Sectioning DONE DONE DONE DONE DONE DONE DONE DONE DONE PENDING

Grinding/ Polishing DONE DONE DONE DONE DONE DONE DONE DONE DONE PENDING

Nital Etching DONE DONE DONE DONE DONE DONE DONE DONE DONE PENDING

Vickers Hardness Measurement

DONE DONE DONE DONE DONE PENDING DONE DONE DONE PENDING

Inclusion Size Measurement

DONE PENDING DONE DONE DONE DONE DONE DONE DONE PENDING

Le Pera Etching DONE DONE DONE DONE DONE DONE DONE DONE DONE PENDING

Modified Sodium Metabisulfite

PENDING PENDING DONE DONE DONE PENDING PENDING PENDING PENDING PENDING

Modified Le Pera Etching PENDING PENDING PENDING PENDING PENDING PENDING PENDING PENDING PENDING PENDING

SEM Inclusions analysis PENDING PENDING DONE DONE DONE PENDING PENDING PENDING PENDING PENDING

SEM Microstructure PENDING PENDING DONE DONE DONE PENDING PENDING PENDING PENDING PENDING

SEM-FEC (WDS) PENDING PENDING PENDING PENDING PENDING PENDING PENDING PENDING PENDING PENDING

Hyper Probe PENDING PENDING PENDING PENDING PENDING PENDING PENDING PENDING PENDING PENDING

Future Work A JEOL JXA-8530F (FEG) "Hyperprobe" electron probe microanalyzer (EPMA-electron microprobe analyzer) will be used in this study.

Specifications: Available WDS analyzing crystals on the five-spectrometer channels are: Gas-flow, P-10: LDE1 6-10 (Ka), 20-29 (La) or TAP 8-15 (Ka), 24-41 (La), 57-80 (Ma) Gas-flow, P-10: LDE2 5-8 (Ka), 20-29 (La) or TAP 8-15 (Ka), 24-41 (La), 57-80 (Ma) Sealed, Xenon: PETJ 13-26 (Ka), 36-66 (La), 71-92 (Ma) or LIF 19-38 (Ka), 48-93 (La) Sealed Xenon: PETL 13-26 (Ka), 36-66 (La), 71-92 (Ma) EDS Detector: JEOL SDD (silicon drift detector ) - Silicon Drift x-ray detector with 10 mm2 active area; 133 eV resolution. Detects Boron thru Uranium.

Atomic % vs. Spot Number

Weight% vs. Spot Number

compositional and structural factors that influence hydrogen … · 2018-06-18 · ferrous physical...

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