Abstract
In this article, we report the results of experimental studies on the impact of ball burnishing parameters on the roughness, microstructure and microhardness of the surface layer of laser-cut C45 steel parts. We also analysed the distribution of residual stresses generated in the surface layer of these parts. Laser-cut parts often require finishing to improve the quality of their surface. The tests performed in this study were aimed at assessing whether ball burnishing could be used as a finishing operation for parts of this type. Ball burnishing tests were performed on an FV-580a vertical machining centre using a mechanically controlled burnishing tool. The following parameters were varied during the ball burnishing tests: burnishing force Fn, path interval fw and the diameter of the burnishing ball dn. Ball burnishing of laser-cut C45 steel parts reduced the surface roughness parameters Sa and Sz by up to 60% in relation to the values obtained after laser cutting. Finish machining also led to the reorganization of the geometric structure of the surface, resulting in an increase in the absolute value of skewness Ssk. This was accompanied by an increment in microhardness (maximum microhardness increment was ΔHV = 95 HV0.05, and the thickness of the hardened layer was gh = 40 µm) and formation of compressive residual stresses in the surface layer.
Highlights
Ball burnishing has been successfully used in the engineering industry for several decades now.It allows one to obtain hardened surfaces with low roughness, improved resistance to abrasive wear and increased fatigue strength [1,2,3]
The surface roughness parameters Sa and Sz were reduced by 21% to 60% relative
The surface roughness parameters Sa and Sz were reduced by 21% to 60% relative to the values obtained after laser cutting
Summary
Ball burnishing has been successfully used in the engineering industry for several decades now. As an effect of the action of the smooth burnishing tool on the workpiece, the material is deformed and thermally plasticized; this mechanism depends on the machining environment [16] The increase in hardness depends on the type of workpiece, machining conditions [4,17,20], and the type of machining environment [21] Another very important effect of ball burnishing is the formation of compressive residual stresses in the surface layer. During finishing with a diamond tool, sliding friction occurs between the tool and the surface of the workpiece This leads to an increase in the temperature of the treated area, which causes phase changes, and an increase in the hardness of the part in the edge zone, relative to its hardness after laser cutting. We performed experiments in which we assessed the impact of ball burnishing on the properties of the surface layer of laser-cut C45 steel parts
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