MICROSTRUCTURE CHARACTERIZATION OF YTTRIUM-MODIFIED REACTIVE-ION-PLATED TI(Y)N COATING BY MEANS OF TRANSMISSION ELECTRON-MICROSCOPY

By means of transmission electron microscopy and microdiffraction techniques, the fine microstructure of the Ti(Y)N coating A3 steel substrate system has been revealed to be a series of sublayers of mixed phases: substrate alpha-Fe; alpha-Fe + Y6Fe23 (sublayer I); FeTi + Y + Ti (sublayer II); Ti2N + YN + Ti(x)N(y) (sublayer III); TiN (columnar crystallites). Sublayer I is about 2000-angstrom thick, sublayer II about 500-angstrom and sublayer III about 1200-angstrom. The phases at the interface areas show the following orientation relations: [1BAR23]alpha-Fe-parallel-to [101]Y6Fe23-parallel-to [012BAR]FeTi (121BAR)alpha-Fe-parallel-to (1BAR21)Y6Fe23-parallel-to (1BAR21)FeTi and [1BAR13]FeTi-parallel-to [0001]Y-parallel-to [1BAR11]Ti2N (21BAR1)FeTi-parallel-to (1BAR1BAR20)Y-parallel-to (011BAR)Ti2N The formation mechanism of the Ti(Y)N\A3 system is also discussed and a structure model is proposed.