Improved wear resistance of P/M tool steel alloy with different vanadium contents after ion nitriding

AISI 1020 steel was plasma nitrocarburized at different gas mixtures (N 2 and H 2 ), 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-Fe 2–3 (C, N) and γ′-Fe 4 (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 mm 3 /N m) was obtained at austenitic nitrocarburizing for 4 h, the lowest friction coefficient ( μ  = 0.35) was also attained at austenitic treatment.

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

Investigation of abrasive + erosive wear behaviour of surface hardening methods applied to AISI 1050 steel

Two-body abrasion of nitrocarburised steels for hydraulic cylinders

Powder metallurgy tool steels are technologically well established, being employed in several applications. However, for certain situations, as in the case of components submitted to severe wear, it is necessary to enhance its surface properties. Among the surface hardening techniques, ion nitriding has proven to be a good candidate for treating powder metallurgy tool steels, since the parts are less susceptible to distortions, as can occur on other conventional surface treatments. The objective of this work was the verification of the effect of vanadium on ion nitriding and, consequently, on wear behavior. The alloys with different vanadium contents were ion nitrided at 550 °C for 1, 3, and 5 h. The nitrided layers were characterized by microhardness test, optical microscopy (OM), scanning electron microscopy (SEM) with energy-dispersive X-ray spectrometry (EDS), X-ray diffraction (XRD), and pin-on-disk test. The hardness values of the layers enhanced significantly after ion nitriding treatment, due to the formation of VN. The wear test revealed that hardness enhancement resulted in a lesser mass loss for a compound layer of VN and γ′-Fe4N. The treatment time did not influence the shape and size of carbides present in these steels.

H.-J. Kim

Papers

The improvement of three-body abrasive wear of plain carbon steel by thermochemical treatments