FABRICATION AND WEAR BEHAVIOR OF PEC/N HARDENED LAYER ON PURE IRON
Abstract
In this paper, the antifriction carbonitriding (PEC/N) layers were prepared on pure iron by cathodic plasma electrolytic treatment (PET) in glycerin and carbamide aqueous solution under 360V for 1, 3 and 10min. Influence of discharge time on morphology, structure, surface roughness and microhardness of PEC/N layer was analyzed. The tribological performance of the PEC/N layer, growth mechanism and diffusion process during PEC/N treatment was investigated. The thickness of the PEC/N layer grew to 48μm for 10min treatment and the growth of the saturation layer met the parabolic law. The highest microhardness of the surface was up to 811 HV, which was 5 times of that of iron substrate. The PEC/N layer consisted of α-Fe, Fe2−3N, Fe4N, Fe3C, Fe5C2 phases and a little FeO phase. The wear rate of the PEC/N layer reduced by five-sixes comparing with the iron substrate and the surface of the wear track was much smoother. The temperature close to the surface during PEC/N fitted by the tested temperature values inside the sample was 801∘C (1074K), and the combination diffusion rate of C and N into pure iron during PET at 360V reached 4.09×10−12m2/s. The electron temperature fluctuates between 3000K and 8000K. The antifriction PEC/N layer displayed a very good wear resistance and the higher diffusion rate makes plasma electrolytic carbonitriding a very effective technique for surface modification of pure iron.
