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

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

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

Internal hydrogen embrittlement GENERALITIES Internal hydrogen embrittlement External hydrogen embrittlement

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

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

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

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

REPORTED ACCIDENTS AND INCIDENTS FAILURE OF A HYDROGEN TRANSPORT VESSEL IN 1983. HYDROGEN CRACK INITIATED ON INTERNAL CORROSION PITS

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

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

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

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

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

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

Specimens for compact tension test TEST METHODS Specimens for compact tension test

TEST METHODS Air Liquide/CTE equipment to perform fracture mechanic test under HP hydrogen (up to 1 000 bar)

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

TEST METHODS Influence of hydrogen pressure by British Steel 10-2 10-3 da 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

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)

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

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

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

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

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

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

Fatigue test - Principle TEST METHODS Fatigue test - Principle

Fatigue test - Pressure cycle TEST METHODS Fatigue test - Pressure cycle

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 H2 + 300 ppm O2 F 0.07 Hertz

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

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

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)

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

PERMEATION TESTS 4.1. Definition 4.2. Important parameter: temperature

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

5.2. Material Heat treatment and mechanical properties

5.2. Material Welding

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

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

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

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

5.3. Design and surface conditions Surface defects FAILURE OF A HYDROGEN TRANSPORT VESSEL IN 1983. HYDROGEN CRACK INITIATED ON INTERNAL CORROSION PITS

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

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

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

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

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