Effect of Centrifugal Shot Peening on the Surface Properties of Laser-Cut C45 Steel Parts

Abstract

This article presents the results of experimental studies of the impact of centrifugal shot peening parameters on the roughness, microstructure, and microhardness of the surface layer of laser-cut C45 steel parts. Residual stress distributions and the presence of iron oxides on the surface of these elements were also examined. Centrifugal shot peening tests were performed on an FV-580a vertical machining center while using a specially designed peening head. The parameters that were varied during centrifugal shot peening included tangential speed of the tool vg and feed rate vf. The use of centrifugal shot peening for finish machining of laser-cut C45 steel parts allowed for obtaining a four-fold reduction in the surface roughness parameters Ra and Rz. As a result of shot peening, the geometrical structure of the surface of the steel parts was modified and it acquired new beneficial features, such as large values of the rounding radii of the micropeaks and high material ratios (Rmrmax = 92%). At the same time, the surface layer was hardened (microhardness increased by 16%) and a compressive residual stress layer was produced on the surface of the workpieces. Additionally, as the shot impacted the processed surface, combustion products were “blasted” or “sheared” off it. Shot peening using the proposed technique can be successfully performed while using CNC machines.

Selected Properties of the Surface Layer of C45 Steel Parts Subjected to Laser Cutting and Ball Burnishing

“…A similar reduction (40% to 94%) in surface roughness parameters was reported for 41Cr4 steel specimens subjected to ball burnishing [ 5 ]. The changes in the values of the roughness parameters obtained in the present experiment are also similar to those reported in [ 42 ]. Centrifugal shot peening of laser-cut C45 steel specimens allowed researchers to reduce the Ra parameter by 46% to 79% and the Rz parameter by 42% to 77% [ 42 ].…”

“…The changes in the values of the roughness parameters obtained in the present experiment are also similar to those reported in [ 42 ]. Centrifugal shot peening of laser-cut C45 steel specimens allowed researchers to reduce the Ra parameter by 46% to 79% and the Rz parameter by 42% to 77% [ 42 ]. The finding that centrifugal shot peening led to larger changes in roughness parameters is associated with the fact that the burnishing elements used in the two processes impact the surface of the workpiece in different ways.…”

“…Flash can be removed from the bottom edge of a workpiece using hand files, deburring machines, wire brushes and belt sanders. The geometric structure of laser-cut surfaces and their properties can be improved by using centrifugal shot peening [ 42 ], smoothing with diamond tools [ 43 ], or mechanical grinding [ 44 ].…”

“…Centrifugal shot peening of laser-cut parts [ 42 ] leads to the reorganization of the geometric structure of their surface, endowing it with favourable features. Parts finished by centrifugal shot peening had over four times lower surface roughness parameters and a 14 times higher material ratio.…”

“…A review of the literature shows that laser-cut surfaces require finishing. The methods used so far in finishing laser-cut parts produce surface defects [ 43 , 44 ], generate tensile stress in the surface layer [ 44 ], and often require the use of expensive special tools [ 42 ]. The beneficial effect of ball burnishing on the state of the surface layer of parts with a hardness above 45 HRC is well known, but there are no studies showing that this method could be applied in the processing of laser-cut parts.…”