BUSCADOR RECOLECTA

This study reports the synthesis and characterization of ternary Cr-Al-O and quaternary Cr-Al-O-N coatings deposited by cathodic arc physical vapour deposition, for various nitrogen and oxygen mass flow ratios during the growth process. The composition, microstructure, indentation hardness and modulus of the films have been characterized by scanning electron microscopy, electron probe micro-analysis, X-ray diffraction, and nanoindentation techniques. The evolution of the microstructure and mechanical properties of the coatings after ambient air annealing from 800 °C up to 1100 °C have been investigated. As the oxygen to nitrogen mass flow increases, the as-deposited coatings exhibit lower hardness, higher roughness, lower crystallinity and a more marked columnar structure. At oxygen to nitrogen mass flow ratios bigger than 10/90, the coatings exhibit a stoichiometry of the type (CrAl)2+εO3−ε. Only the coatings with an oxygen to nitrogen mass flow ratio smaller than 10/90 retained nitrogen in their compositions. In all cases, the coatings developed a cubic fcc lattice structure. After annealing at 1100 °C the resulting microstructure showed a clear dependency upon the initial composition of the films. The evolution of the microstructure during the high temperature tests, as well as the analysis of the nanoindentation hardness, composition and thickness also provided valuable information about the combined effects of the thermal stability and the oxidation of the deposited coatings., This work has been funded by the Spanish Ministry of Economy and Competitiveness through the project PROTEOX MAT2013-45391-P. The European Commission is also acknowledged through the FP7-FOFNMP project MICROFAST under contract Nr 608720. The Research Group of Surface Engineering and Nanostructured Materials in the Universidad Complutense de Madrid also acknowledges financial support of the Spanish MINECO (project MAT2015-65539-P).

In this work CrAlO and CrAlO/CrAlN multilayers deposited by cathodic arc evaporation are evaluated as protective films in metal and ceramic powder FAST sintering tool dies fabricated in titanium-zirconium-molybdenum allows (TZM). The films have been characterised in terms of their composition, microstructure, mechanical properties and thermal stability in air at high temperatures between 800 °C and 1100 °C; in addition the tribological performance has been analysed at room temperature and at 400 °C. The crystalline structure and composition of the CrAlO based coatings are compatible with the formation of a mixture of α-corundum and a cubic fcc (Cr,Al)2O3. The crystalline structure of the multilayer is, on the other hand, dominated by the cubic fcc lattice plane reflections of the CrAlN. The deposited specimens have high hardness, between 25 and 30 GPa, which are stable even after annealing at 1000 °C. Even more, the multilayer coating also exhibited good mechanical stability at 1100 °C. The multilayer coating also exhibited an excellent behaviour against wear at 400 °C. Sintering trials using coated TZM dies have been carried out using Ti90Sn10 and Al2O3 high energy ball milled powders. The experimental results show that the oxide based coating formulations are potentially able to protect the tools from wear, sticking and oxidation of their surfaces. This may allow the use of TZM material as an alternative to other substrates such as graphite., The authors acknowledge the financial support of the European Commission through the FP7 Grant Agreement 608720 (Micro-FAST), and the MINECO (Spain) in the frame of the PROTEOX project (MAT2013-45391-P).