Surface Hardening of BN Coated Commercially Pure Titanium due to Laser Irradiation

Abstract

Surface hardening behavior of BN coated commercially pure titanium was investigated after laser irradiation or the vacuum-heating. BN film was coated on c.p. titanium by using a dynamic mixing method. After that, CO₂ laser beam was irradiated on the specimens for various times up to 40 s. Vacuum-heating was performed on the specimens at 1173 K for various time. The Ti-B-N solid solution phase containing precipitates of TiB and Ti₂N was formed by CO₂ laser irradiation and vacuum-heating. The surface hardness of the heated specimens was 35∼40 GPa. The surface of the specimens was smooth and had no cracks.
The influence of the composition and the thickness of the B-N film on the surface hardening behavior was also investigated. The B-coated c.p. titanium in either case of the laser irradiation or the vacuum-heating had the smaller hardness and many surface cracks. The surface hardening behavior of BN₂-coated c.p. titanium induced by vacuum-heating was similar to that of BN coated one.