Surface integrity of rotary ultrasonic machined ZrO2–TiN and Al2O3–TiC–SiC ceramics

Al2O3 and ZrO2 based ceramics are extremely difficult to manufacture, being rotary ultrasonic machining (RUM) an interesting machining process for these materials. In this work the effect of RUM on the final surface integrity of ZrO2–TiN and Al2O3–TiC–SiC ceramics has been studied. During RUM of these ceramics two material removal modes co-exist: brittle and ductile fracture. In Al2O3–TiC–SiC prevails the ductile fracture mode whereas in ZrO2–TiN the brittle fracture mode predominates. Lower surface roughness is obtained if diamond tools with smaller grain size are used, the axial depth of cut is reduced and/or the feed rate is increased. RUM generates compressive surface residual stresses in both ceramics. Machining parameters have no effect on final residual stresses in ZrO2–TiN, but in Al2O3–TiC–SiC more compressive stresses are generated when feed is reduced and/or axial depth of cut is increased. RUM of ZrO2–TiN does not induce any detrimental tetragonal → monoclinic phase transformation of ZrO2.