Effect of Shot Peening Parameters on the Properties of Surface Layers in AISI 4140 in Different Heat Treatment Conditions

Author:  H. Hozapfel, A. Wick, O. Vohringer
Source:  The Shot Peener magazine, Vol 10/Issue 1, March 1996
Doc ID:  1996116
Year of Publication:  1996
Abstract:  
The effects of the technical important shot peening parameters peening pressure, mass flow, hardness and size of the shot particles on the surface layers properties were systematically studied. Samples of the difficulty heat treated steel AISI 4140 with a hardness between HV230 and HV660 were shot peened. The surface layers were characterized by measuring the residual stresses and the half width values of interference ines using X-ray diffraction and by determining the surface roughness. With increasing workpiece hardness characteristic maxima of the compressive residual stresses beneath the surface are observed. An increasing peening intensity causes a deeper penetration of the compressive residual stresses. During shot peening the half values near the surface increase for softer material conditions, whereas these values decrease for harder material conditions. This caused by a multiplication of dislocations in the softer material and by a rearrangement of dislocations of high density to energetically more favorable positions in the harder material.