Curtiss-Wright Surface Technologies is an industry leader in shot peening, a cold working process in which small spherical media called shot bombard the surface of a part. During the shot peening process, each piece of shot that strikes the material acts as a tiny peening hammer; this imparts a small indentation or dimple to the surface. To create the dimple, the surface of the material must yield in tension. Below the surface, the material tries to restore its original shape, thereby producing a hemisphere of cold-worked material highly stressed in compression below the dimple.
Nearly all fatigue and stress corrosion failures originate at the surface of a part, but cracks will not initiate or propagate in a compressively stressed zone. Because the overlapping dimples from shot peening create a uniform layer of compressive stress at metal surfaces, shot peening provides considerable increases in part life. Compressive stresses help increase resistance to fatigue failures, corrosion fatigue, stress corrosion cracking, hydrogen assisted cracking, fretting, galling and erosion caused by cavitation. This enables component designs to achieve their maximum potential. The maximum compressive residual stress produced just below the surface of a part by shot peening is at least as great as one-half the yield strength of the material being shot peened.
In most modes of long-term failure, the common denominator is tensile stress. Tensile stresses attempt to stretch or pull the surface apart and may eventually lead to crack initiation. Because a compressive layer slows crack growth significantly, increasing the depth of this layer increases crack resistance.
Shot peening is the most economical and practical method of ensuring surface residual compressive stresses. For applications that require deeper residual compressive stresses than those provided by shot peening, CWST’s laser peening process imparts a layer of beneficial compressive stress that is four times deeper than that attainable from conventional shot peening treatments.
Shot peening also can induce the aerodynamic curvatures in metallic wing skins used in advanced aircraft designs. Additional applications for shot peening include work hardening through cold work to improve wear characteristics, closing of porosity, improving resistance to intergranular corrosion, straightening of distorted parts, surface texturing and testing the bond strength of coatings.
CWST engineering specialists can help you best address the fatigue, forming and distortion correction challenges that manufacturers of fabricated metal parts face every day. MIC’s shot peening facilities employ the latest state-of-the-art processing capabilities for shot peening components of diverse shapes, sizes and materials under rigidly controlled conditions.
Shot Peening Animation
CWSTfacilities are capable of meeting most industry standard shot peening specifications, including:
Note: To download copies of AMS Specifications, go to the SAE Website at: