Dry sliding of plasma-sintered iron—The influence of nitriding on wear resistance

Samples of unalloyed iron were sintered in the presence of an abnormal glow discharge using the confined anode–cathode configuration in order to allow surface enrichment of the sample with atoms from the cathode. AISI 430 and AISI 1020 cathodes were used to sinter the iron with and without Cr enrichment, respectively. The chromium favors the formation of a hard compound layer after nitriding (with a microhardness up to 1300 HV) due to the presence of chromium nitrides. In order to evaluate the wear resistance and surface damage to the samples, dry sliding wear tests were carried out using a block-on-ring system with applied normal loads of 25–150 N. A large scatter in the experimental results was observed for the unnitrided samples. This effect was attributed to the capacity of the materials to undergo a severe-to-mild wear transition during sliding. Nitriding was found to reduce the wear rate by at least one order of magnitude. In particular, the nitrided samples enriched with chromium (540 °C) did not display any damage at 25 N, the lowest normal load used in the present investigation.