NANOSMAT 2007 - INTERNATIONAL CONFERENCE ON SURFACES, COATINGS AND NANOSTRUCTURED MATERIALS Structure and mechanical properties of gradient coatings deposited by PVD technology onto the X40CrMoV5-1 steel substrate K. Lukaszkowicz Æ L. A. Dobrzan ´ski Received: 28 June 2007 / Accepted: 31 January 2008 / Published online: 21 February 2008 Ó Springer Science+Business Media, LLC 2008 Abstract This paper presents the research results on the structure and mechanical properties of gradient coatings deposited by PVD methods on the X40CrMoV5-1 steel substrate. The tests were carried out on TiAlN, TiCN and AlSiCrN coatings. It was found that the structure of the PVD coatings consisted of fine crystallites, while their average size fitted within the range of 15–50 nm, depending on the coating type. The coatings demonstrated columnar structure as well as good adherence to the sub- strate, the latter not only being the effect of adhesion but also by the transition zone between the coating and the substrate, developed as a result of diffusion and high- energy ion action that caused mixing of the elements in the interface zone. The critical load L C2 lies within the range of 46–59 N, depending on the coating type. The TiAlN coatings demonstrate the highest hardness and abrasive wear resistance. The good properties of the PVD gradient coatings make them suitable in various engineering and industrial applications. Introduction For several decades, tool material designers have been trying to develop and produce an ideal tool material of high ductility and maximum possible wear resistance charac- teristics in working conditions. Such combination is practically impossible to obtain. Therefore, various attempts were made to find at least a partial solution to the issue, by creation of layer structures, the methods included without limitation of thermal–chemical treatment, com- posite material production and monolayer coating deposition by the CVD and PVD methods as well as overlaying welding or hard layer spraying by the spray metallization method [1–5]. Each of these methods, how- ever, represents restrictions caused by inappropriate thickness of the surface layer, and, particularly, the issues due to the inappropriate adhesion of the layer produced or the excessive stresses between the surface layer and the substrate. Such stresses often cause accelerated layer spalling or chipping, especially when superposition occurs between the internal structural stresses and external ones caused by loads developed in working conditions. Gradient coatings deposited on the tool material sub- strate and providing appropriately high resistance to abrasive wear in tool operating conditions, core ductility and stress relaxation between the particular coating layers and between the gradient coating and tool material coating are seen as a solution to the issue [6–8]. Functional gra- dient coatings create a new class of coatings with properties and structure changing gradually. Frequently a rapid difference between the coating and substrate prop- erties occurs causing a stress concentration in this area, both during the manufacturing and operation of the tools. This causes fast degradation demonstrated by cracks and delamination of the coatings. The application of functional gradient coatings offers a possible solution to the issue. Gradient coatings can be applied in manufacturing modern machining tools, due to their resistance to high-temperature oxidation and erosion as well as abrasive wear. Two groups can be identified within the range of applications of gradient coatings [9, 10]: K. Lukaszkowicz (&) Á L. A. Dobrzan ´ski Institute of Engineering Materials and Biomaterials, Silesian University of Technology, Konarskiego St. 18A, 44-100 Gliwice, Poland e-mail: krzysztof.lukaszkowicz@polsl.pl 123 J Mater Sci (2008) 43:3400–3407 DOI 10.1007/s10853-008-2523-3