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C. Blawert, B. L. Mordike, G. A. Collins, K. T. Short, Y. Jirásková, O. Schneeweiss and V. Perina, “Characterisation of Duplex Layer Structures Produced by Simultaneous Implantation of Nitrogen and Carbon into Austenitic Stainless Steel X5CrNi189,” Surface and Coatings Technology, Vol. 128-129, 2000, pp. 219-225.
ABSTRACT: AISI 321 austenitic stainless steel was treated using rf plasma carbonitriding with the intention of use low-cost orthopedic implant material in biomedical applications. The treatment process was carried at low working gas pressure of 0.075 mbar in nitrogen-acetylene gaseous mixture to form a superficial carbonitrided layer. The samples were treated using rf inductively coupled at a fixed plasma-processing power of 500 W and for a processing time varied from 4 to 20 minutes. The microstructural, mechanical and tribological properties of the untreated and treated samples were studied. The surface hardness is improved by rf plasma carbonitriding to a maximum of 1468 HV0.1 for plasma-processing time of 16 min. To evaluate the biocompatibility performance, the blood was cultured in RPMI media to test the adhesion of blood cells on the untreated and treated samples. It has been found that the blood adhesion on the treated samples is enhanced with increasing the plasma-processing time. The contact angle of the carbonitrided surfaces is decreased to lower values compared to that of the untreated surface. Furthermore, the carbonitrided layer in-vitro corrosion was tested in Ringer’s solution. A degradation in the corrosion resistance was observed for the sample carbonitrided at low plasma processing time of 4 min. However, the corrosion resistance increased to a maximum value at a plasma-processing time of 8 min then gradually decreased with further increase of plasma processing time.