Tribological and Microstructural Insights into CNC Surface Grinding of Tool Steels: Effect of Grinding Parameters on Surface Integrity

This study explores the tribological and microstructural responses of OHNS and EN24 tool steels subjected to CNC surface grinding under dry conditions using two abrasive wheels—aluminum oxide (Al₂O₃) and silicon carbide (SiC). The effects of grinding parameters—wheel speed, depth of cut, and table speed—on surface roughness (Ra) and subsurface integrity were evaluated through a full factorial experimental design. Surface characterization using a contact profilometer was supported by analysis of variance (ANOVA) to assess statistical significance. Results demonstrated that wheel speed and depth of cut significantly influenced surface roughness (p < 0.05), with OHNS showing better finish using SiC and EN24 exhibiting enhanced response with Al₂O₃. SEM revealed key wear-related microstructural changes, including micro-grooving, ploughing, and crack suppression. EDX identified oxide film formation and abrasive grain embedment, suggesting the development of transient tribo-layers. While no direct wear tests were performed, wear behavior was qualitatively inferred from surface topography and microstructural features—offering predictive insight into abrasive and adhesive wear resistance under optimized grinding conditions. These findings provide mechanistic insights into grit–workpiece interaction and tribological contact evolution, offering practical guidance for surface engineering of tool steels in high-performance applications.