Effect of material structure on spinel machinability in its fixed abrasive lapping

Clarifying the effects of material properties on the lapping performance is helpful in optimizing the lapping processing and revealing the lapping mechanisms. In this study, the microstructures of single-crystal spinel (SS) and polycrystalline spinel (PS) were observed by a microscope after being etched with H3PO4 at high temperature. Automatically controlled micro-hardness testing and analysis systems were used to measure the hardness and crack length of SS and PS wafers. On this basis, the fracture toughness and critical cutting depth were estimated. And, a series of lapping tests were conducted to evaluate the effects of crystals on its machinability with a fixed abrasive pad (FAP). After lapping, the size distribution of collected debris was measured by using a laser particle analyzer. The debris and selected posts of FAP were observed by using a scanning electron microscope. Experimental results indicate that the different microstructures and hardness characteristics between SS and PS result in different average cutting depths, which finally affect the lapping debris sizes, FAP surface conditions, and its machinability.