Environmental And Metallurgical Factors Of Stress Corrosion Cracking In High Strength Steels

Delayed failures of martensitic high-strength steels in aqueous environments were studied to determine the effect of environmental and metallurgical variables on the mechanisms of stress corrosion. The effects of chloride content, specimen geometry, and polarization potential on the delayed failure of AISI 4340 (235 and 207 Ksi strength level) and HP 9-4-45 (242 Ksi strength level) steels were evaluated. Incubation time for slow crack growth and crack growth rates were measured at various combinations of applied stress and environment using change of resistance and compliance measurements on precracked center-notch tensile and cantilever loaded notch bend specimens. (Author).

The problem of stress corrosion cracking (SCC), which causes sudden failure of metals and other materials subjected to stress in corrosive environment(s), has a significant impact on a number of sectors including the oil and gas industries and nuclear power production. Stress corrosion cracking reviews the fundamentals of the phenomenon as well as examining stress corrosion behaviour in specific materials and particular industries. The book is divided into four parts. Part one covers the mechanisms of SCC and hydrogen embrittlement, while the focus of part two is on methods of testing for SCC in metals. Chapters in part three each review the phenomenon with reference to a specific material, with a variety of metals, alloys and composites discussed, including steels, titanium alloys and polymer composites. In part four, the effect of SCC in various industries is examined, with chapters covering subjects such as aerospace engineering, nuclear reactors, utilities and pipelines. With its distinguished editors and international team of contributors, Stress corrosion cracking is an essential reference for engineers and designers working with metals, alloys and polymers, and will be an invaluable tool for any industries in which metallic components are exposed to tension, corrosive environments at ambient and high temperatures. Examines the mechanisms of stress corrosion cracking (SCC) presenting recognising testing methods and materials resistant to SCC Assesses the effect of SCC on particular metals featuring steel, stainless steel, nickel-based alloys, magnesium alloys, copper-based alloys and welds in steels Reviews the monitoring and management of SCC and the affect of SCC in different industries such as petrochemical and aerospace

High-strength steels are susceptible to delayed cracking under suitable conditions. Frequently such a brittle failure occurs at a stress that is only a fraction of the nominal yield strength. Considerable controversy exists over whether such failures result from two separate and distinct phenomena or whether there is but one mechanism called by two different names. Stress-corrosion cracking is the process in which a crack propagates, at least partially, by the stress induced corrosion of a susceptible metal at the advancing tip of the stress-corrosion crack. There is considerable evidence that this cracking results from the electrtrochemical corrosion of a metal subjected to tensile stresses, either residual or externally applied. Hydrogen-stress cracking is cracking which occurs as the result of hydrogen in the metal lattice in combination with tensile stresses. Hydrogen-stress cracking cannot occur if hydrogen is prevented from entering the steel, or if hydrogen that has entered during processing or service is removed before permanent damage has occurred. It is generally agreed that corrosion plays no part in the actual fracture mechanism. This report was prepared to point out wherein the two fracture mechanisms under consideration are similar and wherein they differ. From the evidence available today, the present authors have concluded that there are two distinct mechansims of delayed failure. (Author).

Weldment cracking is a broad complex field. Even if one considers only cracking of steel weldments, the problems range from cracking at temperatures near the solidus during welding to cracking at room temperature days, weeks, or months after welding is completed. Numerous reports of investigations in this field are contained in the published and unpublished literature. However, most of these reports cover only a particular problem in a specific area of the broad field of weldment cracking. This review attempts to cover the major aspects of the entire field of weldment cracking. Necessarily, the review is for the most part general, only being specific in a few instances to illustrate a point. (Author).

The chemical environment and metallurgical structure play important roles in the entry of hydrogen into iron and steel. In particular, the effect of compounds of sulfur, arsenic, phosphorus, selenium, and other elements, generally called 'cathodic poisoners, ' is considered. The role of pH, electrochemical potential, stress, and temperature on the hydrogen entry kinetics is also considered. Metallurgical factors that influence the hydrogen entry and permeation rates include the alloy composition (substitutional and interstitial atoms), annealing and tempering (temperature, time), grain size, and the microstructure (form and distribution of carbides, etc.). The literature regarding the stress corrosion cracking of high-strength steel is reviewed. Studies of slow crack growth in gaseous environments are reviewed, with a comparison of crack growth behavior in both gaseous and aqueous media.