Comparison study of plasma oxynitrocarburising and QPQ for 45 steel

Abstract

QPQ (quench-polish-quench) is recognized as an effective surface modification technology which can improve the corrosion and wear resistance of metal materials. However, it is environmentally constrained in real application. In order to explore an environmental friendly and efficient surface modification technology, PNCO (plasma oxynitrocarburising) was developed and compared with QPQ technology for 45 steel. The cross-sectional microstructure, phase composition, microhardness profile, wear and corrosion resistance were tested and analyzed by optical microscopy, SEM, XRD, microhardness tester and wear tester etc. The results show that a compound layer thickness of 20.14 μm and effective hardened layer thickness of 59 μm, surface hardness of 760HV0.05, wear rate of 1.39×10-3 g·N-1·m-1 and corrosion mass loss rate of 0.39% were obtained by PNCO. The XRD results demonstrate that PNCO treated samples mainly contain FexN compound and Fe3O4 oxide. A comparative study between PNCO and QPQ shows that the sectional microhardness, wear and corrosion resistance of the treating layers are the same level. The study provides a feasible research area for environmentally efficient surface modification technology.

Keywords

• 45 steel
• pnco
• qpq
• wear resistance
• corrosion resistance