One way of obtaining increased resistance to stress corrosion cracking is by creating compressive stresses (via shot peening) on the metal surface.

One way of obtaining increased resistance to stress corrosion cracking is by creating compressive stresses (via shot peening) on the metal surface.

• A. True
• B. False
• C. By annealing
• D. By etching

Answer: (A)

Creating a compressive surface layer lowers the effective tensile stress at the surface, which is where stress corrosion cracking tends to start and grow in a corrosive environment. Shot peening achieves this by blasting the metal with small particles, which plastically deform the surface and leave a residual compressive stress field that extends a short distance below the surface. That compressive layer counteracts the tensile stresses that drive crack initiation and propagation, making it harder for cracks to form or advance under stress and corrosion conditions. In addition, the surface becomes harder, which can further resist crack initiation. Annealing, by contrast, tends to relieve residual stresses, including beneficial compressive ones, so it can reduce this protective effect. Etching changes surface appearance or reveals microstructure but does not induce the beneficial compressive residual stresses that shot peening provides. So using shot peening to create surface compression is a valid method to increase resistance to stress corrosion cracking.

Creating a compressive surface layer lowers the effective tensile stress at the surface, which is where stress corrosion cracking tends to start and grow in a corrosive environment. Shot peening achieves this by blasting the metal with small particles, which plastically deform the surface and leave a residual compressive stress field that extends a short distance below the surface. That compressive layer counteracts the tensile stresses that drive crack initiation and propagation, making it harder for cracks to form or advance under stress and corrosion conditions. In addition, the surface becomes harder, which can further resist crack initiation.

Annealing, by contrast, tends to relieve residual stresses, including beneficial compressive ones, so it can reduce this protective effect. Etching changes surface appearance or reveals microstructure but does not induce the beneficial compressive residual stresses that shot peening provides.

So using shot peening to create surface compression is a valid method to increase resistance to stress corrosion cracking.