The investigation of structural, mechanical and tribological properties of plasma nitrocarburized AISI 1020 steel

AISI 1020 steel was plasma nitrocarburized at different gas mixtures (N2 and H2), for various times (1, 2, 4, 8 and 12 h) and at elevated temperatures (500, 570 and 640 °C). The structural, mechanical and tribological properties of nitrocarburized steel were analyzed using X-ray diffraction, microhardness tester, scanning electron microscopy, optical microscopy and pin-on-disk tribotester. The results have shown that the compound layer was composed of ɛ-Fe2–3(C, N) and γ′-Fe4(C, N) iron carbonitrides and the thickness of this layer increased with increasing temperature and time. The nitrocarburizing process affected the surface properties and diffusion layer. It was seen that the surface hardness increased about two times depending on process parameters, and the highest hardness was observed on austenite layer obtained at austenitic treatment (640 °C). The wear strength increased between 20% and 60% depending on the process parameters. While the highest wear strength (1.89 × 10− 5 mm3/N m) was obtained at austenitic nitrocarburizing for 4 h, the lowest friction coefficient (μ = 0.35) was also attained at austenitic treatment.