Dual Shot Peening To Maximize Beneficial Residual Stresses In Carburized Steels

Author:  Ahmad, Aquil and Donald, E. Crouch,
Source:  ASM Conf. July, 1989
Doc ID:  1989004
Year of Publication:  1989
Abstract:  
Recent advances in shot peening technology have resulted in the development of a two stage process to maximize the beneficial surface residual stresses induced in hardened, carburized steel, such as SAE 8620, a material commonly used for gears. Steel samples with an effective case depth of 0.72mm (0.029in) were used. Shot peening conditions investigated included: a) single shot peening with: regular hardness steel shot (HRC 45-55), hard steel shot (HRC 55-62), and b) dual peening, first with hard steel shot followed by either smaller diameter hard steel shot at a lower intensity, or smaller diameter glass beads at lower intensities. To investigate the near surface effects initially observed, two samples were dual peened after surface layer removal (0.13mm-0.29mm). Comparing the residual stress profiles obtained, the following observations were made: use of higher hardness shot produces higher magnitude residual stresses, dual peening produces higher magnitude residual stresses; shot peening after the removal of the surface upper transformation products results in increased surface residual compressive stresses for similar shot peening parameters.