Increase the hardness of polycrystalline cubic/wurtzite boron nitride composite through hybrid laser/waterjet heat (LWH) treatment

The material, boron nitride (BN), is chemically and thermally stable which is desirable for high-speed machining in demanding chemical and thermal environments. Although BN’s hardness is lower than that of single polycrystalline diamond, a novel laser/waterjet heat treatment process provides a new approach to increase the hardness of the dual-phase 50% cubic and 50% wurtzite (cBN/wBN) composite close to or as high as diamond’s hardness. Results indicate that experimentally measured hardness increase is dependent on the processing parameter such as laser fluence and overlap between heat treatment passes. Statistical analysis is carried out to identify the processing parameter that result in maximum hardness increase.