Tribological behavior of candidate coatings for Al die casting dies

Candidate coatings on H13 steel substrates aimed at improving the tribological performance of die casting dies for the Al foundry industry have been extensively characterized. The study is part of a comprehensive research program whose objective is to design a multilayer coating system that encompasses all the requirements to provide increased surface die performance and die life. The coatings investigated were: CrC, CrN (2), ZrN, MoNx, MoZrN, TiAlN, TiN/TiC, TiB2/TiC, NiAl, NiAlN, MoSiC/SiC, Ti–B–C–N, Cr3Si and a control sample that was subjected to a carbonitriding thermochemical treatment. The characterization included: scratch testing, wear testing+optical profilometry, microhardness, optical microscopy and X-ray diffraction. Several wear behavior and adhesion behavior modes were identified based on the morphological characteristics of the wear and scratch marks, and the results of the tests. Wear and adhesion properties seem to be related and mainly controlled by the brittle or tough nature of the coating as well as by the nature of the substrate/coating interface, to a lesser degree by coating hardness, and only marginally by the coating coefficient of friction and roughness. Only a few of the candidate coatings had concomitant good wear and adhesion performance.