Evaluation of Hard TiN Coatings by Depth Sensing Indentation and Scratch Testing Methods |
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Authors: | Ridha Berriche Ashok K Koul Peter Au Jean-Pierre Immarigeon |
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Affiliation: | (1) National Research Council, Institute for Aerospace Research, M-13A, Ottawa, Canada, K1A 0R6 |
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Abstract: | The IAR Nanomechanical Probe (NMP) was used in the depth sensing indentation mode to evaluate the Vickers hardness (HV) and elastic modulus E of five commercial TiN coatings applied to a 17-4 PH stainless steel substrate. The HV values of the TiN layers at depth to thickness (DTT) ratios of less than 0.1 varied between about 28 and 39 GPa, depending on the deposition process. The elastic modulus was within the range of 300 to 400 GPa, corresponding to published values, at DTT ratios of less than or equal to 0.05. At higher DTT values, the elastic modulus decreased with increasing DTT ratio due to larger and larger interference from the less rigid stainless steel substrate. Depth sensing scratch tests were also performed on the samples to determine the critical load crvalues needed to cause spallation of the coatings. For each coating, the interfacial fracture toughness Kic was calculated from crand used to describe the adhesive strength. Distinct differences between the Kic values of the different samples were observed, reflecting differences in adhesive strength. The significance of these results is discussed in terms of the application of titanium nitride coatings to gas turbine engines. |
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Keywords: | adhesion hardness nanoindentation scratch TiN |
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