Shot peening is a process for cold working surfaces by bombarding the product with shot of a solid and spherical nature propelled at a relatively high velocity. In general, shot peening will increase the fatigue life of a product that is subject to bending or torsional stress. It will improve resistance to stress corrosion cracking. It can be used to form parts or correct their shapes. See Appendix X1 for additional information.

It is essential that the shot peening process parameters be controlled rigidly to ensure repeatability from part to part and lot to lot.

This specification covers techniques and methods necessary for proper control of the shot peening process.

This specification covers the requirements for automated, controlled shot peening of metallic articles prior to electrolytic or autocatalytic deposition of nickel or chromium, or as a final finish, using shot made of cast steel, conditioned cut wire, or ceramic media. The process is applicable to those materials on which test work has shown it to be beneficial within given intensity ranges. It is not suitable for brittle materials. Hand peening and rotary flap peening are excluded specifically. Shot peening induces residual compressive stresses in the surface and near-surface layers of metallic articles, controlling or limiting the reduction in fatigue properties that occurs from nickel or chromium plating of the article, or the fatigue properties of unplated articles. It is a process for cold working surfaces by bombarding the product with shot of a solid and spherical nature propelled at a relatively high velocity. Cast steel, cut wire, and ceramic shot shall all be spherical in shape and shall all be free of sharp edges, corners, and broken pieces. Prior to shot peening, the following operations shall be done first: heat treatment, machining, grinding, flaw test, crack test, corrosion detection, cleaning, and masking. Peened surfaces shall be uniform in appearance and completely dented so that the original surface is obliterated entirely. After shot peening, the following methods shall be done: residual shot removal, surface finishing, chemical cleaning of nonferrous metals and their alloys, thermal and heat treatments, and corrosion protection.