1. Chapter E: Hydrogen embrittlement Hervé Barthélémy – Air Liquide
and permeation
Belfast – January 25, 2013
Hervé Barthélémy – Air Liquide

2. INTRODUCTION - GENERALITIES
HYDROGEN EMBRITTLMENT AND PERMEATION
INTRODUCTION - GENERALITIES
REPORTED ACCIDENTS AND INCIDENTS ON HYDROGEN EQUIPMENT
TEST METHODS
PERMEATION TESTS

3. PARAMETERS AFFECTING HYDROGEN EMBRITTLEMENT OF STEELS
HYDROGEN EMBRITTLMENT
AND PERMEATION
PARAMETERS AFFECTING HYDROGEN EMBRITTLEMENT OF STEELS
- Environment, Design and Material
HYDROGEN EMBRITTLEMENT OF OTHER MATERIALS
HYDROGEN ATTACK
CONCLUSION - RECOMMENDATION

4. Internal hydrogen embrittlement
GENERALITIES
Internal hydrogen embrittlement
External hydrogen embrittlement

5. GENERALITIES Hydrogen attack Gaseous hydrogen embrittlement
1 - COMBINED STATE :
Hydrogen attack
2 - IN METALLIC SOLUTION :
Gaseous hydrogen embrittlement

6. GENERALITIES Important parameter : THE TEMPERATURE
T  200°C Hydrogen embrittlement
T  200°C Hydrogen attack

7. GENERALITIES Reversible phenomena Transport of H2 by the dislocations
CRITICAL
CONCENTRATION AND
DECOHESION ENERGY
H2 traps

8. FAILURE OF A HYDROGEN TRANSPORT VESSEL IN 1980
REPORTED ACCIDENTS
AND INCIDENTS
FAILURE OF A HYDROGEN TRANSPORT VESSEL IN 1980

9. REPORTED ACCIDENTS AND INCIDENTS
FAILURE OF A HYDROGEN TRANSPORT VESSEL IN HYDROGEN CRACK INITIATED ON INTERNAL CORROSION PITS

10. HYDROGEN CYLINDER BURSTS INTERGRANULAR CRACK
REPORTED ACCIDENTS
AND INCIDENTS
HYDROGEN CYLINDER BURSTS INTERGRANULAR CRACK

11. OF A HYDROGEN STORAGE VESSEL
REPORTED ACCIDENTS
AND INCIDENTS
VIOLENT RUPTURE
OF A HYDROGEN STORAGE VESSEL

12. H2 VESSEL. HYDROGEN CRACK ON STAINLESS STEEL PIPING
REPORTED ACCIDENTS
AND INCIDENTS
H2 VESSEL. HYDROGEN CRACK ON STAINLESS STEEL PIPING

13. TEST METHODS Static (delayed rupture test) Constant strain rate
Fatigue
Dynamic

14. TEST METHODS Fracture mechanic (CT, WOL, …) Tensile test Disk test
Other mechanical test (semi-finished products)
Test methods to evaluate hydrogen
permeation and trapping

15. Fracture mechanics test with WOL type specimen
TEST METHODS
Fracture mechanics test with WOL type specimen
Vessel head
Specimen
O-rings
Vessel bottom
Gas inlet – Gas outlet
Torque shaft
Load cell
Instrumentation feed through
Crack opening displacement
gauge
Knife
Axis
Load application

16. Specimens for compact tension test
TEST METHODS
Specimens for compact tension test

17. TEST METHODS
Air Liquide/CTE equipment to perform fracture mechanic test under HP hydrogen (up to bar)

18. TEST METHODS
10-4
10-5
10-6
10-7
10-8 20 25 30
Influence of hydrogen pressure (300, 150, 100 and 50 bar) - Crack growth rate versus K curves

19. TEST METHODS Influence of hydrogen pressure by British Steel 10-2 10-3da dN
mm/cycle
10-2
Influence of
hydrogen pressure
by British Steel
10-3 X
152 bar
41 bar
1 bar
165 bar H2
10-4 N2
10-5 10 20 30 40 N2 60 80
100
K, MPa Vm

20. TEST METHODS
Tensile specimen for hydrogen tests (hollow tensile specimen) (can also be performed with specimens cathodically charged or with tensile spencimens in a high pressure cell)

21. TEST METHODS I = (% RAN - % RAH) / % RAN I = Embrittlement index
RAN = Reduction of area without H2
RAH = Reduction of area with H2

22. Cell for delayed rupture test with Pseudo Elliptic Specimen
TEST METHODS
Pseudo Elliptic
Specimen
Cell for delayed rupture test
with Pseudo Elliptic Specimen

23. Tubular specimen for hydrogen assisted fatigue tests
TEST METHODS
Inner notches
with elongation
measurement
strip
Tubular specimen for hydrogen assisted fatigue tests

24. Disk testing method – Rupture cell for embedded disk-specimen
TEST METHODS
Disk testing method – Rupture cell for embedded disk-specimen
Upper flange
Bolt Hole
High-strength steel ring
Disk
O-ring seal
Lower flange
Gas inlet

25. Example of a disk rupture test curve
TEST METHODS
Example of a disk rupture test curve

26. TEST METHODS I
m (MPa)
Hydrogen embrittlement indexes (I) of reference materials versus maximum wall stresses (m) of the corresponding pressure vessels

27. Fatigue test - Principle
TEST METHODS
Fatigue test - Principle

28. Fatigue test - Pressure cycle
TEST METHODS
Fatigue test - Pressure cycle

29. Fatigue tests, versus  P curves
TEST METHODS
Fatigue tests, versus  P curves
nN2
nH2 1 2 3 4 5 6 7 8 9 10 11 12 13
Delta P (MPa)
Cr-Mo STEEL
Pure H2
H ppm O2
F 0.07 Hertz

30. Principle to detect fatigue crack initiation
TEST METHODS
Fatigue test
Principle to detect fatigue crack initiation

31. TESTS CHARACTERISTICS
Type of hydrogen embrittlement and transport mode
TESTS
LOCATION OF HYDROGEN
TRANSPORT MODE
Disk rupture test
External
Dislocations
F % test
External + Internal
Diffusion + Dislocation
Hollow tensile specimen test
Fracture mechanics tests
P.E.S. test
Tubular specimen test
Cathodic charging test
Diffusion

32. Practical point of view
TESTS CHARACTERISTICS
Practical point of view
TESTS
SPECIMEN
(Size-complexity)
CELL
COMPLEMENTARY
EQUIPMENT NEEDED
Disk rupture test
Small size and very simple
Hydrogen compressor and high pressure vessel
Tensile test
Relatively small size
Large size
Tensile machine
Fracture mechanics test
Relatively large size and complex
Very large size and complex
Fatigue tensile machine for fatigue test only
P.E.S. test
Average size and very easy to take from a pipeline
Average size --
Tubular specimen test
Large size and complex
No cell necessary
Large hydrogen source at high pressure
Cathodic charging test
Small size and simple
Electrochemical equipment (potentiostat)

33. TESTS CHARACTERISTICS
Interpretation of results
TESTS
TESTS SENSIBILITY
POSSIBILITY OF RANKING MATERIALS
SELECTION OF MATERIALS – EXISTING CRITERIA
PRACTICAL DATA TO PREDICT IN SERVICE PERFORMANCE
Disk rupture
High sensitivity
Possible
Yes
PHe/PH2
Fatigue life
Tensile test
Good/Poor sensitivity
Possible/Difficult
Yes/No
Treshold stress
Fracture mechanics
Good sensitivity
No, but maximum allowable KIH could be defined
- KIH
- Crack growth rate
P.E.S. test
Poor sensitivity
Difficult No
Tubular
specimen test
Cathodic
charging
Possible but difficult in practice
Critical hydrogen concentration

34. PERMEATION TESTS
4.1. Definition
4.2. Important parameter: temperature

35. 4.1. Definition
Permeability is the result of gas solution and gas diffusion
Permeability coefficient is defined as follows :
Pe = S × D.
Permeation in polymers is a molecular permeation

36. 4.1. Definition The permeability coefficient is defined as the product
of the diffusion and solubility coefficients of the gas
for this material. When Henry’s law is satisfied, the flow
at steady state, for a given temperature, is given by:
J: flow of molecules going through a surface A, at steady state (permeability flow rate)
e: thickness of the sample
PM: partial pressure of the gas on the upstream side
PV: partial pressure of the gas on the downstream side
Pe: permeability coefficient of the gas A P M V e J 2
<<A

37. 4.2. Important parameter: Temperature
According to Arrhenius
Permeability investigated mainly for elastomer
and plastic materials
Hydrogen permeability of metals is several order
of magnitude lower than permeability of polymers

38. PERMEATION CELL BY GASEOUS CHARGING
Reference electrode (S.C.E.)
Argon (inlet)
Argon (outlet)
Auxiliary electrode (Pt)
Teflon cell
Disk (working electrode)  58 mm and e = 0,75 mm

39. PERMEATION TEST BY CATHODIC CHARGING - PRINCIPLE
Battery
Recorder
Potentiostat
Reference electrodes
Solution
Auxiliary electrodes (Pt)
Membrane
Charging solution

40. PERMEATION AND DEGASSING CURVES - PRINCIPLE
Hydrogen flow
Theorical curve (with D0)
2nd permeation
Stop in charging
Calculation
Beginning
1st permeation
Beginning (charging)

41. 5.3. Design and surface conditions
PARAMETERS AFFECTING
HYDROGEN EMBRITTLEMENT OF STEELS
5.1. Environment
5.2. Material
5.3. Design and surface conditions

42. 5.1. Environment or “operating conditions”
Hydrogen purity
Hydrogen pressure
Temperature
Stresses and strains
Time of exposure

43. Influence of oxygen contamination
5.1. Environment or “operating
conditions”
Hydrogen purity
Influence of oxygen contamination

44. Influence of H2S contamination
5.1. Environment or “operating
conditions”
Hydrogen purity
Influence of H2S contamination

45. Influence of H2S partial pressure for AISI 321 steel
5.1. Environment or “operating
conditions”
Hydrogen pressure
Influence of H2S partial pressure for AISI 321 steel

46. Influence of temperature - Principle
5.1. Environment or “operating
conditions”
Temperature
Influence of temperature - Principle

47. Influence of temperature for
5.1. Environment or “operating
conditions”
Temperature
Influence of temperature for
some stainless steels

48. 5.1. Environment or “operating conditions”
Hydrogen purity
Hydrogen pressure
Temperature
Stresses and strains
Time of exposure

49. 5.2. Material Microstructure Chemical composition
Heat treatment and mechanical properties
Welding
Cold working
Inclusion

50. 5.2. Material
Heat treatment and mechanical properties

51. 5.2. Material
Welding

52. 5.2. Material Microstructure Chemical composition
Heat treatment and mechanical properties
Welding
Cold working
Inclusion

53. 5.3. Design and surface conditions
Stress level
Stress concentration
Surface defects

54. Crack initiation on a geometrical discontinuity
5.3. Design and surface conditions
Stress concentration
Crack initiation on a geometrical discontinuity

55. Crack initiation on a geometrical discontinuity
5.3. Design and surface conditions
Stress concentration
Crack initiation on a geometrical discontinuity

56. 5.3. Design and surface conditions
Surface defects
FAILURE OF A HYDROGEN TRANSPORT VESSEL IN HYDROGEN CRACK INITIATED ON INTERNAL CORROSION PITS

57. HYDROGEN EMBRITTLEMENT OF OTHER MATERIALS
All metallic materials present a certain
degree of sensitive to HE
Materials which can be used
Brass and copper alloys
Aluminium and aluminium alloys
Cu-Be

58. HYDROGEN EMBRITTLEMENT OF OTHER MATERIALS
Materials known to be very sensitive to HE :
Ni and high Ni alloys
Ti and Ti alloys
Steels : HE sensitivity depend on exact
chemical composition, heat or mechanical
treatment, microstructure, impurities
and strength
Non compatible material can be used at
limited stress level

59. HYDROGEN ATTACK Nelson curves Legend : Surface decarburization
Internal decarburization
(Hydrogen attack)
Nelson curves

60. HYDROGEN ATTACK In addition to parameters summarized on the
« Nelson curves » (influence of P, T, Cr and Mo):
Ti and W have also a beneficial effect
C, Al, Ni and Mn (excess) have a
detrimental effect
Other parameters :
Heat treatment
Stress level, welding procedure

61. CONCLUSION - RECOMMENDATION
The influence of the different parameters shall
be addressed.
To safely use materials in presence of
hydrogen, an internal specification shall
cover the following :
The « scope », i.e. the hydrogen pressure, the temperature and the hydrogen purity
The material, i.e. the mechanical properties,
chemical composition and heat treatment
The stress level of the equipment
The surface defects and quality of finishing
And the welding procedure, if any