The CrNx coatings were deposited by arc ion plating on Ti-6Al-4V substrates.The impacts of the coating conditions,including the nitrogen partial pressure,deposition rate,duty cycle of the voltage pulse,on mechanical properties of the coating were evaluated.The microstructures of the coating were characterized with scanning electron microscopy,X-ray diffraction,and transmission electron microscopy.The results show that the nitrogen partial pressure significantly affects the surface morphologies,microstructures and mechanical properties of the CrNx coatings.For example,as the partial pressure rises up,the coating becomes increasingly smooth with decreased number and sizes of Cr droplets.At a 1.0 Pa of nitrogen,the Cr2N phase transited into CrN.Moreover,the partial pressure influenced the bombardment of charged particles and the electronic properties of the surface.At 1.5 Pa,CrN and a high deposition rate,highly compact,nanocrystal CrN films with high surface hardness can be grown.
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