高密着性α-Al_2O_3膜被覆切削工具のミクロ組織 Microstructure of Highly Adhesive TiN-Ti(C, N)-bonding layer-α-Al_2O_3 Films Coated by CVD on Cemented Carbide Cutting Tools
The microstructure of highly adhesive CVD coated α-Al<SUB>2</SUB>O<SUB>3</SUB> films on cemented carbide cutting tool inserts have been investigated. These inserts are coated with a TiN layer, a MT(moderate temperature)-Ti(C, N) layer, a bonding layer, and a α-Al<SUB>2</SUB>O<SUB>3</SUB> layer by using CVD.<BR>SEM, TEM, and TEM-EDX were used to characterize the coatings, and following characteristics were found.<BR>(1) The bonding layer is composed of Ti, C, N, and O or of Ti, C, and O. Its crystal structure is a face centered cubic one with a lattice parameter of 0.431nm.<BR>(2) Each grain in the bonding layer continues crystallographically from the MT-Ti(C, N) layer grains.<BR>(3) There are crystalline planes running between a grain of the bonding layer and a grain of the a-Al<SUB>2</SUB>O<SUB>3</SUB> layer.<BR>(4) Vertical-plane-shape projections are formed on the surface of bonding layer.<BR>The last three characteristics are considered to be the cause for improved α-A1<SUB>2</SUB>O<SUB>3</SUB> layer adherence and longer tool life.<BR>A crystallographical model shows that the above mentioned microstructure is consistent to X-ray diffraction result which shows the (110) plane of α-Al<SUB>2</SUB>O<SUB>3</SUB> layer is oriented to the parallel of the insert's surface.
粉体および粉末冶金 46(4), 422-426, 1999-04-15
Japan Society of Powder and Powder Metallurgy