Structural, mechanical and tribological behavior of different DLC films deposited on plasma nitrided CF170 steel

In order to improve the surface hardness and tribological properties of CF170 steel, a duplex treatment including plasma nitriding and deposition of different diamond-like carbon (DLC) films was carried out on CF170 steel. The structural, mechanical and tribological properties of untreated, plasma nitrided and duplex-treated samples were investigated by methods of XRD, SEM, AFM, Raman spectroscopy, XPS, hardness tester, scratch tester and ballon-disc tribometer, respectively. Raman spectroscopy and XPS revealed that the Ti/a-C/(ta-C) film had the highest amount of sp3 content, followed by Cr/WC/(a-C:H) and Cr/WC/(a-C:H:W) films. The hardness of duplextreated samples was significantly higher than that of single plasma nitrided sample and the highest value was obtained from the Ti/a-C/(ta-C) film deposited on the plasma nitrided sample. The critical adhesion load (Lc3) of the Cr/WC/(a-C:H) film deposited on the plasma nitrided sample was obviously higher than that of the Ti/a-C/ (ta-C) film deposited on the plasma nitrided sample. The duplex-treated samples showed a low friction coefficient. Both Cr/WC/(a-C:H) and Ti/a-C/(ta-C) films deposited on plasma nitrided samples had a low wear rate. The wear rate of the Cr/WC/(a-C:H) film deposited on the plasma nitrided sample was reduced by one (five) orders of magnitude compared to the plasma nitride (untreated) sample.

Automated summary

The duplex treatment of plasma nitriding and deposition of different diamond-like carbon films significantly improved the hardness and reduced the wear rate of CF170 steel. Additionally, it resulted in a low friction coefficient, showing promise for enhancing the tribological properties of the material.