Talking about stress corrosion cracking and its prevention

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The cracking of an alloy under the combined action of corrosion and tensile stress in a certain direction is known as stress corrosion cracking. There are two types of crack morphology: those that develop along grain boundaries, known as intergranular fracture ； Cracks that penetrate through the grains are known as transgranular fractures; there are also mixed types, where the main crack is intergranular while the secondary cracks or tips are transgranular. This is one of the most dangerous forms of corrosion, capable of causing sudden accidents. Stress corrosion cracking has several characteristics: ① Tensile stress must be present (such as residual stress generated by welding or cold working); compressive stress can suppress this type of corrosion ； ②It only occurs in certain systems, such as austenitic stainless steel/C1-system, carbon steel/NO-3 system, copper alloys/NH+4 system, etc. The methods to prevent stress corrosion include the following: performing heat treatment to eliminate stresses in the components ； Improve the design structure to prevent stress concentration in specific areas; the loads selected in the design should be below the critical value that leads to stress corrosion ； Surface shot peening generates compressive stress, with electrochemical protection, coatings, or corrosion inhibitors being used.