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Parts made of zirconia ceramics have been used in various high-end fields, and some of these parts exhibit complex styles with various curved surfaces. As a prominent machining technique for manufacturing zirconia ceramic parts, tangential ultrasonic-assisted grinding has mainly been employed in improving the processing efficiency and simultaneously ensuring the surface quality. With the aim of further improving the processing performance of tangential ultrasonic-assisted curved surface grinding, the effects of the grinding paths with α = 0°, α = 45°, and α = 90° on the surface quality and profile of a workpiece were studied for a specific curved surface, and the wear of the grinding wheel with different paths was analyzed. In addition, the material removal mechanisms were discussed for single diamond grit grinding tests. The obtained results demonstrated that (1) the surface roughness Sa was different at different grinding paths, i.e., at different values of α, and the surface finish mainly depended on the ultrasonic amplitude. (2) The profile error of the curved work-surface was different at different values of α. (3) The wear of the grinding wheel at α = 45° was the most serious, and at α = 0° and α = 90°, the abrasive grain wear was slight. These tendencies agreed with the case of the work-surface quality. (4) The material removal mechanism was different with and without ultrasonics, which resulted in the differences in the work-surface finish.

Inconel 718 has been widely investigated due to its machining properties. The purpose of this work was to investigate a novel proposed grinding technique for Inconel 718 with a combination of ultrasonic-assisted grinding and hydrogen embrittlement (HE) treatment. The technique was hence named hydrogen embrittlement-enhanced ultrasonic-assisted grinding (HEUAG). Before grinding, a thin stress layer was formed on the surface of the workpiece. To reveal its fundamental performance in the grinding of Inconel 718, experiments were conducted to investigate the effect of ultrasonic vibration on the grinding forces and the surface roughness in the presence of hydrogen embrittlement. To investigate the material removal process for HEUAG, single-grit grinding tests were also conducted with hydrogenated samples. Furthermore, the subsurfaces for HEUAG samples were obtained with the transmission electron microscope (TEM) micrographs. The HE treatment reduced the generation of burrs around the scratches and improved the surface quality after grinding.

Zirconia ceramics have been used in the field of smartphone manufacturing, especially for the phone shells. To improve the machining efficiency and simultaneously obtain a mirror-surface quality on the curved surface made by zirconia ceramics, the tangential ultrasonic-assisted grinding (TUAG) was proposed, in which the ultrasonic vibrations of the grinding wheel are always in the direction tangential to the work surface at the grinding point. To reveal the fundamental grinding characteristics of the TUAG on the zirconia ceramic curved surface, the processing principle and according experimental setups were given out at first. The effects of the proposed method on the surface morphology and surface roughness were investigated experimentally and analyzed numerically under different process parameters for plane workpieces. Finally, a curved surface was successfully processed by the novel method with the optimized experimental conditions. The obtained results demonstrated that (1) typical sinusoidal cutting traces appeared on the work surface, which implied that the surface morphology was affected significantly by the ultrasonic vibrations; (2) the surface roughness was distinctly affected by the amplitude of the grinding wheel, and a higher efficiency was attained on the surface quality enhancement when the larger amplitude was applied, e.g., Ra was reduced by 58.3% when an amplitude of Ap–p = 4.66 μm was imposed; and (3) the Ra value in the direction vertical to the wheel feed direction on the curved surface decreased to 39.5 nm, implying that a mirror curved surface can be obtained by TUAG with the appropriate process conditions.