Microscopic Study of Surface Hardening by Grit Blasting on Hot Rolled Low Carbon Steel (SPHC)

Abstract

The effect of grit blasting on the surface and depth properties of hot rolled low carbon steel was investigated. The residual stress depth profile and dislocation density of the specimen were determined using X-ray diffraction. Dislocation density was evaluated by modified Williamson-Hall / modified Warren-Averbach method. Both dislocation density and hardness are highest at the blasted surface and reduce gradually with depth. Compressive residual stress is induced in the blasted surface having a maximum value at a depth of 60 µm from the top surface. This is followed by a steady decrease of compressive stress with depth and finally become tensile. In this experiment, the square root of the dislocation density is proportional to the hardness, and the hardness of the top surface, which could not be measured due to the roughness of the surface, can be estimated. The coefficient α in the Bailey-Hirsch equation was derived from the slope obtained by plotting the shear stress calculated from the hardness against the square root of the dislocation density.