Comparative Tribological Performance of MgO and Cr₂O₃ Modified Zirconia-Toughened Alumina Cutting Tools in Dry Turning of AISI 1045 Steel

This study evaluates zirconia-toughened alumina (ZTA) ceramic tools modified with MgO and Cr₂O₃ for dry turning of AISI 1045 steel. Inserts were fabricated from an 80 wt% Al₂O₃–20 wt% ZrO₂ matrix via powder metallurgy and pressureless sintering. Machining tests were performed at a cutting speed of 200 m/min, feed rate of 0.125 mm/rev, and depth of cut of 0.5 mm according to ISO 3685:1993. Both ZTA–MgO and ZTA–Cr₂O₃ achieved comparable tool lives of 354 ± 2 s and 355.5 ± 1.8 s, respectively, based on three independent tests for each composition. However, differences were observed in the wear morphology and wear progression. ZTA–Cr₂O₃ exhibited a more stable and uniform flank-wear pattern, with no observable built-up edge (BUE), notch wear, chipping, or flaking under the investigated conditions. In contrast, ZTA–MgO showed more pronounced adhesive wear, metallic transfer layers, and non-uniform flank wear. These observations suggest that the Cr₂O₃-modified tool provided more stable wear progression during dry turning of AISI 1045 steel. However, the observed behaviour may result from the combined effects of additive chemistry, microstructure, and sintering conditions. These findings indicate that similar tool life does not necessarily imply identical wear mechanisms, emphasizing the importance of wear morphology in evaluating ZTA ceramic cutting tools for sustainable dry machining.