MICROSTRUCTURE AND PROPERTIES OF (TI,AL)N COATING ON HIGH-SPEED STEEL

(Ti,Al)N coating has been produced on the surface of M2 high speed ste el by the hollow cathode discharge deposition process. The microstruct ure and component depth profiles of the (Ti, Al)N coating have been in vestigated by scanning electron microscopy, X-ray diffraction, transmi ssion electron microscopy and X-ray photoelectron spectroscopy. A 50 n m film of TiO2, oxide layer on the surface of the (Ti,Al)N microstruct ure was formed. There was a transition layer at the interface between (Ti,Al)N and the matrix which consisted of alpha-Ti and FeTi phases. T he experiments on the (Ti,Al)N coating showed that the microhardness a nd wear resistance increased with increasing matrix temperature. In a certain range of nitrogen dow rate the microhardness and wear resistan ce also increased with increasing nitrogen flow rate, which was attrib uted to a crystallographically preferred orientation of the (111) plan e and a denser microstructure. Compared with TiN coating, the oxidatio n resistance of (Ti,Al)N coating was improved as a result of a decreas e in oxidation rate caused by the formation of Al2O3.