Manufacture of Wear-Resistant Alloy Co-Cr-Mo for Medical Implant Applications by Nitriding Coating Method

Abstract

Nitrogen doped as-cast Co-Cr-Mo alloy with markedly enhanced hardness and wear resistance was successfully produced by pack nitriding process. Nitriding proses used the in-pack process using urea fertilizer as a nitrogen source. It was carried out with variations in temperature of 400°C, 500°C, 600°C and followed by annealing. The wear resistance of the specimen is tested using pin-on-disk. The total sample will be soaked in the lactic acid solution for 3 days. The results obtained from the After nitriding process, the hardness of of speciment N400 obtained a hardness value of 261.54 HV speciment N500 of 309.68 HV, and speciment N600 of 429.14 HV, the results of the hardness value increased in each speciment. The wear resistance value obtained for each speciment N400, N500, N600 is 2,81 x 10-6 mm3/Nm, 7,50 x 10-7 mm3/Nm, 1,87 x 10-7 mm3/Nm. The nitriding process forms a layer on the surface of the as-cast Co-Cr-Mo, it’s called Layer of Cr-N which is the result of heating/decomposing urea fertilizer into nitrogen gas which can coat the surface so that Cr-N bonds are formed in the layer. The thickness of the Cr-N layer on the N400 specimen is 0.28 mm, N500 is 0.35 mm, N600 is 0.38 mm. In addition, the surface results that have been tested for wear resistance form quite fine scratches but the formation of abrasions, such as abrasion, abrasion groove, delamination, and cohesive failure