The effect of rapid thermal processing (RTP) on TiN coatings deposited by PVD and the steel-turning performance of coated cemented carbide

Monolithic TiN coatings deposited onto cemented carbide cutting tool insert s coated by PVD methods have been subjected to pulsed intense electron beam treatments in the energy range 3-5 J cm(-2). The temperature profiles for this rapid thermal process (RTP) covered the range between fusion of the co balt binder in the carbide to surface fusion of the TiN coatings. The treat ment caused extensive cracking and removed the atomic level defects, vacanc ies and dislocations, and residual stress. There was some nitrogen loss ver y close to the surface but no change in the stoichiometry of the bulk of th e nitride. No changes were found in the microstructure of the carbide subst rate below the coatings. Steel-turning tests showed that treatment of the c oatings at the lowest power used, 3 J cm(-2), reduced the flank wear by a f actor of about two. (C) 1999 Elsevier Science S.A. All rights reserved.