Development of Supertough Ceramic or Cermet Thick Coatings Available in Various Surroundings

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Austenitic type 304 stainless steel was ion-nitrided and subsequently ion-plated with Cr-Ni-N whose Ni content was varied from 0 at% to 50 at%, utilizing the conventional AIP (arc ion plating) source. The ceramic film of CrN coated onto the pre-nitrided steel demonstrated good wear resistance even under a heavy load. Furthermore, a 10μm thick CrN film exhibited the least wear among the 3 to 19μm thick CrN films. The Cr-Ni-N films containing Ni were composed of mixed phases of Cr^*N and Ni.Cr^*N is a newly observed Cr nitride that may contain some Ni and has been identified as an f.c.t.structure. A Cr-Ni-N film with Ni content of 11 at% coated onto the pre-nitrided steel demonstrated the best wear resistance among the CrN film or Cr-Ni-N films with high Ni content. This superior wear resistance was maintained even at film thicknesses exceeding 20μm, unlike the tendency of CrN film.Furthermore the Cr-Ni-N thin films were deposited on the untreated or pre-nitrided steels utilizing a modified AIP source in order to reduce the number of macroparticles in these deposited films. The films deposited by the modified AIP source exhibited a higher nitrogen concentration than the films prepared by the conventional AIP source. The Cr-Ni-N films coated onto the pre-nitrided steels with a low Ni content demonstrated the lowest friction coefficient and the best wear resistance among these films. Furthermore, it was found that the films with a high Ni content exhibited the superior wear resistance without the pretreatment of nitriding.As for the corrosion resistance, the CrN film or Cr-Ni-N films with a low Ni content showed the best corrosion resistance among these films.