Research On Preparations And Properties Of CrN Based Coatings

As the excellent performance of high hardness, good wear resistance and oxidation resistance, hard coatings can broaden the use of traditional materials when applied to the surface of materials. In order to develop more useful hard coatings, in this article CrSiN and CrHfSiN coatings were synthesized on the basis of CrN coating. Analysized structure and performance of all the coatings, the main research results were as follow:(1) CrN coating was prepared by DC magnetron sputtering and the influence of N2 flow and bias voltage were studied. The results showed that the grains decreased and the consistency of CrN coating increased when any factor of the two increasing. CrN coating was mainly composed by CrN, Cr2N and Cr, and no obvious dominant orientation was exist. The hardness of coating reduced with the increasing N2 flow, while improved with the increasing bias.(2) CrN coating was prepared by high pulse power magnetron sputtering and the influence of pulse width was studied. The coating deposited by this means the internal cohesion of grains were strengthened and crystal growth orientation were enhanced. The adhesion of coatings increased first then reduced with the increasing pulse width, whie the hardness was always increasing in the process.(3) CrSiN coatings were prepared by the introduction of Si. The deposition conditions of CrSiN coating:N2/Ar=18:12, Pu=600 W, VB=-50 V, P=0.5 Pa, T=200℃. CrSiN coating was composed by CrN and Cr, With the increase of Si, the coating deposition rate decreased, while the hardness first increased then decreased. Compared with CrN coating, CrSiN coating had lower friction coefficient and higher adhesion and hardness. When the Si content was 1.13%, coating hardness was higher than 4200HV0.01. Only the outer coating was oxidized when it’s 800℃, so the coating can protect the substrate well; The outer coating oxidized seriously when it’s 900℃, and generated a defect extending into the inner coating, but the coating still can protect the substrate.(4) The surface of CrHfSiN coating was dense, the cross section morphology showed it’s still columnar crystal. CrHfSiN coating was mainly composed of CrN, and also contained some CraN and HfN. When it’s oxidized at 800℃ and 900℃, the phase in coating was Cr2N and Cr2O3. A dense oxide film formed inside the coating during the oxidation, prevent O diffusing into the inner coating and substrate, thus protecting substrate from oxidation. After the oxidation at 1000℃, phases in coating were Cr2O3 and Fe2O3, the coating was oxidized seriously, increasing stress in coating made it peeled, resulting in the oxidation of substrate.