CrN coatings were prepared on M2 high-speed steel and Si chips by an ion beam enhanced deposition(IBED)technique with varying
nitrogen ion bombarding energy.The CrN coatings on Si chips were used to characterize micro-mechanical and structural properties, such as
microhardness,fracture toughness(K_ 1C),
microstructure and composition,with nano-indentation,microhardness test,X-ray diffraction spectrometry,X-ray photoelectron spectroscopy and electron probe microanalysis techniques.The CrN coatings on M2 steel were employed to measure their tribological properties in ambient air of 50% relative humidity(RH) and de-mineralized water with a fretting wear tester.The results show that microhardness of the CrN coatings increases with increasing bombarding energy from 4 to 12 keV.Coversely,K_ 1C value of the coatings decreases with increasing the bombarding energy.These results can be attributed to the increase of nitrogen content in the coatings with increasing the nitrogen ion bombardment energy.Whereas the Cr/N ratio is greater than one at 4 keV,the ratio is smaller than one at 8 keV and 12 keV.Fretting wear tests indicate that the CrN coatings can significantly lower the firction coefficient,and improve the wear resistance of the coated M2 steel in ambient air of 50% RH.However,the CrN coatings do not perform so well in water as in ambient air.The inherent pinholes in the coatings may cause the mutual enhancement of corrosion-wear during the fretting wear tests,thus contributing to the underperformance of the CrN coated steel in aqueous electrolytes.