High-loading 316L stainless steel by integrated low-temperature surface nitriding and DLC deposition

Because of the low hardness of 316L stainless steel, enhancing its surface hardness and wear resistance by coating technologies often produces the "egg-shell effect," resulting in suboptimal coating performance. Although nitriding is an effective method to improve the load-bearing capacity of soft substrates like 316L stainless steel, the high nitriding temperature tends to produce Cr compounds, which deteriorates the corrosion resistance. To address this issue, we describe a novel approach that couples arc-enhanced plasma nitriding with high-energy pulsed biasing to achieve high-efficiency, low-temperature nitriding. Our results indicate that the application of kV-level pulsed bias enables rapid nitriding at a low temperature (400 degrees C) and a nitriding rate of up to 6.5 mu m/ h. The nitrided layer consists mainly of the gamma-N phase without showing the formation of Cr compounds. The hardness of the nitriding layer of 1300 HV provides sufficient bearing capacity for the subsequent deposition of a diamond-like carbon (DLC) layer. The integrated nitriding/DLC-processed substrate shows a low wear rate of 2.55 pound 10-16 m3/N & sdot;m even at ultra-high contact stress of 3.88 GPa. Furthermore, wear resistance is enhanced by nearly 36 times compared to the standalone DLC coating.