Study on Scratching Process of Alumina Ceramic by Diamond Indenter under Compressive Pre-stress

The high hardness and brittleness of engineering ceramics make it difficult to ensure surface quality during conventional grinding. Compressive pre-stress assisted machining, as a new processing technology, can effectively improve the surface/subsurface damage of engineering ceramics. In this study, compressive pre-stress assisted scratching experiment was conducted on 95% Al 2 O 3 ceramics with diamond indenter under three pre-stresses of 0 MPa, 200 MPa and 400 MPa. The influence of compressive pre-stress on the scratch morphology of 95% Al 2 O 3 ceramics, as well as the changes in scratch force and vibration signal during the wear of indenter were comprehensively analyzed. The experimental results show that when the compressive pre-stress increases to 400 MPa, the scratch depth is reduced by 5–15%, the width is reduced by 10–30%, and the depth of scratch subsurface damage is also reduced, avoiding the occurrence of obvious cracks. Wavelet decomposition of the collected vibration signals shows that as the increase of the compressive pre-stress, the fluctuation value of singulars in high-frequency signals gradually decreases, and the percentage of energy gradually increases. Combined with wavelet analysis and the surface wear morphology of indenter, it was found that although the large compressive pre-stress aggravates the tool wear, the surface machining quality of the material is also significantly improved.