Silicon Enhancement of the Compound Layer for Tribological Application of Nitrided Hot-Work Steel

Enhancement of tribological surface properties and thermal stability of nitrided layers is possible when using plasma process doped with silicon containing gasses (PEN Plasma Enhanced Nanostructure). Treatment of small and especially large size metal forming and stamping tools can be realized by application of the latter. In this strategy, the low-friction thin-nanostructured surface is supported by a hard compound-zone that in turn is supported by a large diffusion-zone. The GDMS and XRD analysis were carried out on one of the H-13 samples subjected to this duplex plasma treatment (PEN) revealed that the surface was enriched with silicon, carbon and nitrogen. Mechanical testing carried out on the samples revealed that the properties of the PEN are superior over the properties of the plasma nitrided and over the non-treated H-13 forging steel samples. Results of the scratch test showed that the critical force at which the damage of the surface occurs in PEN sample is much larger ~425 mN than in the PN sample ~258 mN. At the same time the residual depth of the permanent deformation in the PEN sample was smaller, ~0.52 µm as compare to PN sample, ~0.75 µm and, ~1.28 µm for the NN sample. Results of the Pin-On-Disk wear tests showed reduction of friction coefficient for the PEN layers sliding against the 440C stainless steel ball. The reduction in friction was also achieved with PN samples.