Surface layer characterization of shot peened gear specimens

Abstract

The production of gear components includes numerous manufacturing<br/>operations, which are carried out to ensure proper surface characteristics.<br/>Shot peening is one of the surface finishing processes used for transmission<br/>components like gears to improve their fatigue behavior. Shot peening increases<br/>the compressive residual stresses on the surface, and the procedure also reduces<br/>the amount of retained austenite in the surface layer. In addition, shot peening<br/>has an influence on other mechanical properties, such as surface roughness and<br/>surface hardness. An experimental design was conducted with varying shot<br/>peening process parameters, like coverage density and intensity, to alter the<br/>surface layer of 13 transmission gear specimens. The correlation between shot<br/>peening parameters, Barkhausen noise (BN) features, and X-ray diffraction<br/>residual stress measurement was studied. Linear correlation was found between<br/>residual stress and shot peening parameters. The relationship between residual<br/>stress and BN root-mean-square was not evident but was revealed by taking the<br/>ratio of BN measurements at different frequencies. Additionally, BN features, such as peak position, coercivity, and integral area, were found to have a linear trend with the intensity. Along with the aforementioned measurements, other material characterization measurements were also taken. The shot peening coverage density was observed to have a linear relationship with surface roughness values, while an intensity of over 0.6 mm A was noticed to affect the surface hardness. The results obtained can be used in the determination of suitable shot peening parameters to achieve a surface with desired residual stress and other surface properties.