Rapid thermal processing of TiN coatings deposited by chemical and physical vapor deposition using a low-energy, high-current electron beam: Microstructural studies and properties

Monolithic TiN coatings deposited onto cemented carbide cutting tool inserts coated by chemical vapor deposition (CVD) or physical vapor deposition (PVD) methods, respectively were subjected to pulsed intense electron beam treatments in the energy range 3 to 5 J.cm(-2). The temperature profiles for this rapid thermal processing (RTP) covered the range between fusion of the cobalt binder in the carbide to surface fusion of the TiN coatings. The treatment caused extensive cracking in all coatings, removed the atomic level defects, vacancies and dislocations, and the residual stress in the PVD coatings, but caused little change in the CVD coatings. There was some nitrogen loss very close to the surface but no change in the stoichiometry of the bulk of the nitride. In contrast, no changes were found in the carbide substrate below the PVD coatings, but microscopic changes were found immediately below the surface in the carbide under the CVD coatings. Steel turning tests suggest that treatment of the PVD coatings at the lowest power used, 3 J.cm(-2), reduced the flank wear by a factor of 2 but had no effect on any of the CVD coatings.