| Title |
Influence of Gas Composition and Treatment Time on the Surface Properties of AISI 316L Austenitic Stainless Steels During Low-Temperature Plasma Nitrocarburizing Treatment |
| ISSN |
1738-8228(ISSN), 2288-8241(eISSN) |
| Keywords |
Low-temperature plasma nitrocarburizing; expanded austenite; austenitic satinless steel; Low-temperature plasma nitriding |
| Abstract |
The major drive for the application of low-temperature plasma treatment in nitrocarburizing of austenitic stainless steels lies in improved surface hardness without degraded corrosion resistance. The low-temperature plasma nitrocarburizing was performed in a gas mixture of N2, H2, and carbon-containing gas such as CH4 at 450℃. The influence of the processing time (5~30h) and N2 gas composition (15~35%) on the surface properties of the nitrocarburized layer was investigated. The resultant nitrocarburized layer was a dual-layer structure, which was comprised of a N-enriched layer (γN) with a high nitrogen content on top of a C-enriched layer (γC) with a high carbon content, leading to a significant increase in surface hardness. The surface hardness reached up to about 1050 HV0.01, which is about 4 times higher than that of the untreated sample (250 HV0.01). The thickness of the hardened layer increased with increasing treatment time and N2 gas level in the atmosphere and reached up to about 25 μm. In addition, the corrosion resistance of the treated samples without containing Cr2N precipitates was enhanced than that of the untreated samples due to a high concentration of N on the surface. However, longer treatment time (25% N2, 30 h) and higher N2 gas composition (35% N2, 20 h) resulted in the formation of Cr2N precipitates in the N-enriched layer, which caused the degradation of corrosion resistance. |