TITLE:
Effect of rf Plasma Carbonitriding on the Biocompatibility and Mechanical Properties of AISI 321 Austenitic Stainless Steel
AUTHORS:
F. M. El-Hossary, A. M. Abd El-Rahman, M. Raaif, A. A. Seleem, M. Abo El-Kassem
KEYWORDS:
Plasma Carbonitriding; Surface Energy; Wear; Corrosion Resistance; Blood Culture; Protein Adsorption
JOURNAL NAME:
Advances in Materials Physics and Chemistry,
Vol.4 No.2,
February
17,
2014
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.