Fundamentals of Hydrogen Embrittlement (eBook)

M. Nagumo, Sc.D.Professor EmeritusLaboratory of Materials Science and TechnologyWaseda University, Tokyo Japan

Preface 6
Contents 8
Chapter 1: Solid Solution 11
1.1 Solubility 11
1.2 Lattice Location 15
1.3 Partial Molar Volume and Strain Field 16
1.4 Atomistic Calculations of the Heat of Solution 17
References 19
Chapter 2: Hydrogen Trapping and Its Detection 20
2.1 Manifestations and Analyses of Hydrogen Trapping 20
2.1.1 Solid Solubility at Low Temperatures 20
2.1.2 Hydrogen Thermal Desorption Analysis 24
2.2 Partition of Hydrogen Among Different Traps 35
2.2.1 Equilibrium Distribution 35
2.2.2 Kinetics of Hydrogen Trapping 37
2.3 Visualization of Hydrogen Distribution 38
References 41
Chapter 3: Interactions of Hydrogen with Lattice Defects 43
3.1 Dislocations 43
3.1.1 Experimental Results 43
3.1.2 Theoretical Estimation of Hydrogen-Dislocation Interactions 48
3.2 Vacancies 51
3.2.1 Density 51
3.2.2 Vacancy Clusters and Migration 53
3.2.3 Interaction of Hydrogen with Vacancies 56
3.3 Precipitates 64
3.4 Grain Boundaries 67
3.5 Voids and Surfaces 68
References 69
Chapter 4: Diffusion and Transport of Hydrogen 72
4.1 Determination of Diffusion Coefficient 72
4.2 Diffusion Process 75
4.3 Hydrogen Transport by Dislocations 79
4.3.1 Release of Internal Hydrogen 80
4.3.2 Electrochemical Permeation 81
References 83
Chapter 5: Deformation Behaviors 85
5.1 Elastic Moduli 85
5.2 Flow Stress 86
5.3 Stress Relaxation and Creep 93
5.3.1 Stress Relaxation 93
5.3.2 Creep 96
5.3.3 Implications of Surface Effects 98
5.4 Direct Observation of Dislocation Activity 100
5.5 Elastic and Atomistic Calculations 101
5.5.1 Elastic Shielding of Stress Centers 101
5.5.2 Mobility of Screw Dislocations - Atomistic Calculations 104
References 106
Chapter 6: Manifestations of Hydrogen Embrittlement 108
6.1 Tensile Tests 108
6.2 Fracture Mechanics Tests 113
6.2.1 Crack Initiation 114
6.2.2 Crack Growth 119
6.3 Fatigue 122
6.4 Delayed Fracture 129
6.4.1 Factors Affecting Delayed Fracture 129
6.4.2 Incubation Period 131
6.4.3 Effects of Environmental Variations 135
References 138
Chapter 7: Characteristic Features of Deformation and Fracture in Hydrogen Embrittlement 141
7.1 Fractographic Features 141
7.2 Strain Localization and Plastic Instability 155
7.2.1 Strain Localization 155
7.2.2 Plastic Instability 160
7.3 Precursory Damage to Crack Initiation 161
7.3.1 Generation of Damage During Mechanical Tests 161
7.3.2 Effects of Stress History 165
References 168
Chapter 8: Effects of Microstructural Factors on Hydrogen Embrittlement 170
8.1 Dislocation and Slip Configurations 171
8.2 Impurities and Alloying Elements 181
8.3 Heterogeneous Phases 184
8.4 Phase Stability and Deformation Microstructures of Austenitic Stainless Steels 188
8.4.1 Hydrides and Phase Changes 188
8.4.2 Compositional Effects on Hydrogen Embrittlement 191
8.4.3 Fractographic Features 195
8.4.4 Deformation Microstructures 196
References 198
Chapter 9: Mechanistic Aspects of Fracture I ~ Brittle Fracture Models 200
9.1 Internal Pressure Theory 201
9.2 Surface Adsorption Theory 204
9.3 Lattice Decohesion Theory 205
9.3.1 Cohesive Strength 205
9.3.2 Local Stress Intensity Approach 206
9.4 Theories of Intergranular Fracture 208
9.4.1 Interface Decohesion 208
9.4.2 Formation of Incipient Crack - Meaning of Surface Energy in Fracture Criteria 212
9.5 Summary of Brittle Fracture Models 216
References 217
Chapter 10: Mechanistic Aspects of Fracture II~Plasticity-Dominated Fracture Models 219
10.1 Outline of Elemental Concepts of Ductile Fracture 219
10.1.1 Void Nucleation 219
10.1.2 Void Growth and Coalescence 220
10.1.3 Plastic Instability 223
10.2 Hydrogen-Enhanced Localized Plasticity Theory 227
10.3 Adsorption-Induced Dislocation Emission Theory 230
10.4 Autocatalytic Void-Formation and Shear-Localization Theory 231
10.5 Hydrogen-Enhanced Strain-Induced Vacancy Theory 232
10.5.1 Brief Summary of Findings 233
10.5.2 Crack Growth Resistance and its Microscopic Origin 235
10.5.3 Simulation of R-Curve and Strain Localization Near the Crack-Tip 237
10.6 Summary of Ductile Fracture Models 238
References 240