COMPARISON OF MICRO-HARDNESS WITH NANO-INDENTATION HARDNESS IN HARDNESS MEASURING FOR MICRON LEVEL HARD COATING

To verify the accuracy and error extent of micro-hardness when measuring the hardness of hard coatings,the hardness of several-micron-thickness TiN and CrN hard coatings by Ion Beam Assistant Deposition was measured by nano-identation,vickers indentation and knoop indentation methods. It is found that,Hnano>HK>HV,HK results are closer to Hnano than HV results under the same load condition. The smaller the thickness,the bigger the discrepancy of Hnano,HV and HK measurement. With the increasing thickness,HK and HV approach Hnano,when thickness reaches 5.0 μm,HV≈HK≈Hnano. The results show that,for hard-coating soft-substrate model,if thickness (t)>5.0 μm,micro-hardness could reflect the coating hardness with some creditability;if t<5.0 μm,nano-identation should be used avoid using micro-hardness.