This chapter reviews experimental studies of the hydrogen embrittlement of high strength steels. The focus has been on six types of steel, having distinctly different microstructures. The six steel types are the low alloy steels, high toughness secondary hardening steels such as AF1410, hot work die steels, martensitic secondary hardening stainless steels, maraging steels and precipitation strengthened martensitic stainless steels. The susceptibilities of these classes of steel to hydrogen embrittlement as measured by the effects of hydrogen on fracture initiation and subsequent crack growth are discussed when the steels are tested in hydrogen gas, when the hydrogen has been introduced by charging and when the hydrogen embrittlement is associated with stress corrosion cracking in distilled water or salt water.

Hydrogen embrittlement of high strength steels

This module provides information about non-stainless martensitic steels; after a general introduction, discussion is made on chemical composition and properties of common grades of maraging steels. The strengthening mechanism in maraging steels is explained and following this, the factors affecting its toughness behavior are highlighted with special mention of the role of alloying elements on structure and properties of maraging steel. Similarly the composition and properties of medium carbon secondary hardening steels are presented. The strengthening mechanisms of AF1410 and similar steels are explained in details. Factors affecting toughness of this class of steel are also enumerated. Recent efforts on the development of new generation ultrahigh strength steels such as press hardenable steels and nanoscale precipitation strengthened ultrahigh strength high toughness steels are documented.

Martensitic Non-stainless Steels: High Strength and High Alloy

The corrosion product formation and the stress corrosion cracking of brass in different ammonia environments have been observed and characterized. Optical and scanning electron microscopy techniques were used to analyze the corrosion phenomena on the systems. The testing methodology was designed to investigate the variables affecting stress corrosion cracking behaviour, these parameters were: stamp geometry, immersion time, Cl- concentration, pH, copper ions concentration, exposure to vapour/ liquid. From this investigation, stress corrosion cracking of brass was shown to occur most severely in ammonia vapour. The increase of the amount of ammonia and copper ions in the form of copper sulphate was found to increase the corrosion of the brass samples.

/pdf/observations-of-corrosion-product-formation-and-stress-55hvfxm1su.pdf

Observations of Corrosion Product Formation and Stress Corrosion Cracking on Brass Samples Exposed to Ammonia Environments

Effects of the Aged Structure and the Prior Austenite Grain Size on Fracture Toughness of 18Ni Maraging Steels

The nature and distribution of residual stresses are invariably critical for fatigue life with dissimilar material joints often inducing high tensile residual stresses. A fatigue-resistant concept of weld cladding process pipelines, producing compressive residual stresses, is under investigation to examine how these stresses may be influenced. Simplified weld cladding simulations have successfully illustrated the development and distribution of residual stresses through the joint. The study has highlighted the importance of accurate material data for clad and substrate materials with current analysis assumptions in a simple thick-walled pipe discussed. Experimental validation, using ICHD, measured residual stresses with depth on weld clad specimens, resulting in good correlation between simulation and experiment for a nickel-chromium-based superalloy clad on low alloy carbon steel as discussed. Future work, including a full 3D representation of the cladding process and a comparison of residual stress measurement methods, are also discussed.

/pdf/an-experimental-validation-of-residual-stresses-in-weld-clad-37cezx63lb.pdf

An experimental validation of residual stresses in weld clad pipelines

https://apps.dtic.mil/sti/pdfs/AD0702692.pdf

The effect of trace impurities on the stress-corrosion cracking susceptibility and fracture toughness of 18Ni maraging steel

: A general but necessarily brief introductory review of the occurrence, phenomenology and mechanistic theories of stress-corrosion cracking (in the widest sense of the words), in metals and alloys is provided. Those changes which are produced in the surface layers of metals by machining and grinding operations, and which could affect the stress-corrosion susceptibility are discussed. A review of the published data on the experimentally observed effects of machining and grinding on the stress-corrosion performance of the major alloy systems (brasses, low carbon steels, high-strength alloy steels, stainless steels, aluminum alloys and titanium alloy) is presented.

https://apps.dtic.mil/dtic/tr/fulltext/u2/684875.pdf

R.P.M. Procter

Papers

The effect of trace impurities on the stress-corrosion cracking susceptibility and fracture toughness of 18Ni maraging steel

The effects of machining and grinding on the stress-corrosion cracking susceptibility of metals and alloys