THE MICROSTRUCTURE AND CUTTING PERFORMANCE OF TIN-TI (C,N)-a BONDING LAYER-α-Al_2O_3 FILMS COATED CUTTING TOOLS

摘要

We developed cemented carbide cutting tools coated with a layer of TiN, moderate temperature- Ti(C,N), bonding, and αAl_2O)3 by chemical vapor deposition (CVD). Tool life is about twice that of ordinary TiN-Ti(C,N)-TiC-n-Al_2O_3 coating in cutting tests on a cast metal FC-250 due to improved α-Al_2O_3 layer adherence. CVD coatings of cutting tools were studied using X-ray diffraction, SEM,EPMA,TEM,and TEM-EDX, with the following results:(1)Bonding layer grains consisted of Ti,C,N, and O, or of Ti, C ,and O.(2)The crystal structure of the bonding layer phase was face-centered cubic with a lattice parameter of 0.43 nml.(3)Bonding layer grains grew eptaxially on moderate temperature-Ti(C,N) layer grains.(4)No disorder of lattice fringes in interfaces between bonding layer grains and α -Al_2O_3 layer grains was seen. (3)and(4) are considered to be the reason for improved tool life and Al_2O_3 layer adherence.