Research On Thermal Properties Of Hard Coatings Deposited By Magnetron Sputtering

CrN,CrAlN amd CrAlSiN transition metal nitride coatings which are widely used as hard coatings material,have a large scale of applications in tools,decorative materials,molds,biotechnology,aerospace and other aspects because of its high hardness,wear resistance,high resistance to oxidation and other excellent performance.CrN,CrAlN amd CrAlSiN coatings had been synthesized via magnetron sputtering,the effect of Al and Si target power and annealing tempreture had been studied on the surface morphology,composition,microstructure and hardness of the coatings.The surface morphology,composition,microstructure and hardness were characterized by scanning electron microscopy(SEM),X-ray diffraction(XRD)and nanoindentation respectively.As the Al target power increased,the contents of Al in Cr AlN coatings gradually increased,the hardness and elastic modulus of the coatings increased,then the(200)direction diffraction peak enhanced,the diffraction peak shifted to the right,while the coatings surface defects and roughness reduced and tends to densification constantly.As the Si target power increased,the contents of Si in CrAlSiN coatings increased,while the contents of Cr and Al element decreased,coatings hardness first decrease then stay stable and the grains grow along the(200)to achieve the lowest surface energy.No peaks corresponding to crystalline silicon nitride can be identified and the added Si leads to the formation of amorphous Si3N4 and hinder the growth of columnar crystals to refine the grain size.After heat treatment at 800 ? in vacuum,it can be seen a small amounts of cracks on the surface of CrAlSiN coatings,the coatings remains a face-centered cubic structure,and the hardness and elastic modulus of the coatings decreased a little.When the vacuum heat treatment temperature raised to 900 and 1000 ? ?,the coatings surface becomes a large number of crack,coatings face-centered cubic structure disappeared.When the vacuum heat treatment temperature increases from 800 to 1000 ? ?,the Cr,Si element contents of coatings continued to decrease,Al element contents remained stable while Fe contents increased.After heat treatment at 800 ? in air,the CrAlSiN coatings remained face-centered cubic structure,and no oxidation peak appeared.So the coatings had good oxidation resistance.After 1000 ?heat treatment in air,CrAlSiN coatings surface appeared a large area of large-size grains,and cubic structure CrAlN phase peak disappeared,while the oxidation peak of Cr,Al,Fe began to appear.So the overall structure of the coatings collapsed.