Mechanical properties of TiN, ZrN, WC coated film on titanium

Objectives:The aim of this study was to compare friction coefficient, vickers hardness, adhesion strength and surface roughness of coated film with TiN(titanium nitride), ZrN(zirconium nitride) and WC(tungsten carbide) on titanium alloy. Materials and Methods: 16 titanium alloy(Ti-6Al-4V) discs of 12mm in diameter and 1mm in thickness were prepared for this study. TiN, ZrN or WC was respectively coated on titanium alloy discs for each specimen of 3 experimental groups, and each specimen of 1 control group was not coated. Each group was made up of 4 specimens. Sputtering method was used among the PVD techniques available for TiN, ZrN and WC coatings. Friction coefficient, vickers hardness, adhesion strength and surface roughness of each group specimen were measured and observed. SPSS version 10.07 program has been utilized for statics. Results: (1) The magnitude of friction coefficient was greater in order of uncoated group(0.48±0.01), TiN group(0.39± 0.02), WC group(0.31±0.03), ZrN group(0.24±0.01). Friction coefficient of three coated groups was remarkably reduced as compared with that of uncoated group. (2) The magnitude of vickers hardness was greater in order of TiN group(1865.2± 33.8), ZrN group(1814.4±18.6), WC group(1008.5±35.9), uncoated group(313.9±18.9). Vickers hardness of three coated groups was increased as compared with that of uncoated group. (3) The magnitude of adhesion strength was greater in order of TiN group(25.3N±1.6),WC group(18.4N±0.7), ZrN group(14.8N±0.6). (4) ZrN or WC coated specimen showed the homogeneous and smooth surface. However, TiN coated specimen showed the rough surface with some defects. Conclusion: When TiN, ZrN or WC coating applied to the abutment screw, frictional resistance would be reduced and hardness would be increased, as a result, the greater preload and prevention of the screw loosening could be expected.