Effect of Shot Peening Parameters on the Surface Characteristics of Differently Heat Treated AISI 4140

Author:  A Wick, H Holzapfel, V Schulze, O Vohringer
Source:  Conf Proc: ICSP-7 (pg 42-53)
Doc ID:  1999014
Year of Publication:  1999
Abstract:  
The effect of the technically important shot peening parameters peening pressure, mass flow, hardness and size of the shot particles on the surface layer properties were systematically studied. Samples of the differently heat treated steel AISI 4140 (German Grade 42CrMo4) with a hardness between HV 230 and HV 660 were shot peened. The surface layers were characterized the residual stresses and the half width values of interference lines using X-ray diffraction and by the surface roughness. With increasing workpiece hardness characteristic maxima of the compressive residual stresses beneath the surface are observed. An increasng peening intensity causes an increase of the depth where the residual stresses change their sign. During shot peening the half width values near the surface increase for softer material conditions due to a multiplication of dislocations, whereas these values decrease for harder material conditions, which is caused by a rearrangement of dislocations of high density to energetically more favourable positions.