A Study On Chemical Composition,phase Structure And Properties Of TiAlCrN Film System

The research of multi component nitride hard film is becoming more and more perfect.Some two and three component nitride hard films,such as TiN,CrN,TiCrN,TiAlN hard film,have been applied in the field of cutting tools.The four component nitride hard films are still in the research stage and have not yet been applied in the market.CrTiAlN hard film is the better in bonding force among the four component nitride hard films.The present research prepared CrTiAlN hard films with different composition by using Ti-Cr,Al-Ti and Al-Cr targets.In accordance with the pre designed plan to adjust the target currents,three groups of CrTiAlN hard films based on CrN,TiN and AlN,were respectively obtained.By the observation of the microstructure and morphology,the chemical composition,the phase composition,the lattice constant and hardness of the as-deposited CrTiAlN hard films,the roles of the content change of three component Cr,Ti and Al on the film performance were revealed.The results show that the as-deposited CrTiAl N hard films have basically consistent surface morphology,droplet distribution density and film thickness under the condition of basically the same deposition process.By adjusting the combination of the targets and the target currents,the compositions of the three groups of film samples reaches certain regularity.The change of component content does not affect the phase composition of the film.The as-deposited CrN-based,TiN-based and AlN-based CrTiAlN films are all composed of a single(CrTiAl)N phase with f.c.c.structure.The XRD spectrums of the CrTiAlN films showed 5 main diffraction peakswhich are from(111),(200),(220),(311)and(222)planes and the one from the alloy CrTiAl phase.The alloy phase comes from the droplets in the films.(CrTiAl)N phases in the as-deposited CrTiAlN films grew along the preferred orientation of(200)phane.This trend does not change with the film composition.The lattice constants of(CrTiAl)N phases were systematically investigated.The changing regularity of lattice constants with composition was revealed.The actual lattice constants of(CrTiAl)N phases are larger than those calculated by the Vegard law and the lattice constants can be controlled by changing the proportion of the three metal components.In terms of mechanical properties,the presence of hardness inflection point was discovered for each of the as-deposited films in the change range of composition.Basically,when the film is based on the AlN,its hardness was significantly less than the ones of the CrTiAlN hard films based on CrN,TiN.