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Although spinodal decomposition of metastable cubic Ti 1 − x Al x N-based coatings and the underlying mechanisms are widely understood, investigations on the influence of high deposition temperatures are lacking. It is thus the aim of this work to elucidate structure, properties, thermal stability and wear performance of Ti 1 − x Al x N/TiN multilayer coatings sputter deposited on powder-metallurgical high-speed steels at substrate temperatures between 375 and 575 °C. At higher substrate temperatures, sharper column boundaries and sharper transition zones in the multilayer arrangement yield increased hardness in the as-deposited state, while the detrimental formation of wurtzite AlN during vacuum annealing is retarded by 50 °C according to Rietveld refinement of X-ray diffractograms. Tribological tests at room temperature and up to 650 °C corroborate the high potential of increased coating temperatures, while demonstrating the crucial importance of using a substrate material with adequate hot hardness. Cutting tests with coated high-speed steel end mills verify the high temperature deposition approach showing a tool life increase of ~ 40%. [ABSTRACT FROM AUTHOR]

Abstract: Highly adherent carbon nitride (CNx) films were deposited using a novel pretreatment with two high power impulse magnetron sputtering (HIPIMS) power supplies in a master–slave configuration: one to establish the discharge and one to produce a pulsed substrate bias. During the pretreatment, SKF3 (AISI 52100) steel substrates were pulse-biased in the environment of a HIPIMS Cr plasma in order to sputter clean the surface and to implant Cr metal ions. Subsequently, CNx films were prepared at room temperature by DC unbalanced magnetron sputtering from a high purity graphite target in a N2/Ar discharge at 3mTorr. All processing was done in an industrial CemeCon CC800 system. A series of depositions were obtained with samples at different bias voltages (DC and pulsed) in the range of 0–800V. Scanning transmission microscopy (STEM) and high resolution transmission electron microscopy (HRTEM) show the formation of an interface comprising a polycrystalline Cr layer of 100nm and an amorphous transition layer of 5nm. The adhesion of CNx films evaluated by the Daimler-Benz Rockwell-C reach strength quality HF1, and the scratch tests gives critical loads of 84N. Adhesion results are correlated to the formation of an optimal interfacial mixing layer of Cr and steel. [Copyright &y& Elsevier]