AISI 316 austenitic stainless steel was carbonitrided using rf plasma with
purpose of using low-cost orthopedic implant materials in biomedical applications
besides the manufacturing requests. The plasma treatment
process was accomplished at low working gas pressure of 0.075 mbar in
nitrogen-acetylene gaseous mixture. The plasma-processing time was fixed
at 10 min while the plasma-processing power was varied from 450 to 650
watt. The effect of plasma treatment power on the structure, tribological,
mechanical, electrochemical and biocompatibility of AISI 316 has been investigated.
The structural results demonstrated the formation of nitrogen
and carbon solid solutions, chromium nitride, iron carbide and iron nitride
phases in the treated samples. The microhardness of the treated layer
increases with increasing the processing power to reach a maximum value
of approximately 1300 HV0.1 at 600 W which represents more than 6-folds
increase in microhardness in comparison with the untreated matrix. The
wear and corrosion resistance of the treated AISI 316 were enhanced compared
to the untreated one. The friction coefficient was reduced from nearly
0.5 for the untreated substrate to nearly 0.3 for the carbonitrided sample.
The surface energy and wettability of the carbonitrided samples were augmented
as the plasma-processing power increased. Furthermore, the numbers
of grown mesenchymal stem cells are higher for carbonitrided samples
compared to the untreated one. The formation of nitrogen and carbon
solid solution, chromium nitride, iron nitride and iron carbide hard phases
after carbonitriding process is responsible for achieving good mechanical,
tribological, biocompatibility and electrochemical properties for AISI 316
alloys.