The mechanical properties of AlSi coatings made by PVD technology

Abstract

The mechanical properties (microhardness and scratch test) of AlSi coatings made by PVD magnetron sputtering method from alloys with 7-20%Si were compared. Higher concentration of Si increased deformation resistance of the coating, expressed by depth of scratch. Improved mechanical properties had coatings from alloys modified by TiBAl refiner. KEYWORDS: protective coatings, PVD coatings, AlSi alloys Porównano mechaniczne właściwości (mikrotwardość i test rysy) powłok AlSi wykonanych metodą PVD magnetronowego rozpylania stopów o zawartości 7-20% Si. Większe stężenie Si zwiększało opór odkształcania powłok wyrażony głębokością rysy. Lepsze właściwości mechaniczne miały powłoki ze stopów modyfikowanych TiBAl. SŁOWA KLUCZOWE: powłoki ochronne, powłoki PVD, stopy AlSiIn the production of exhaust systems in the automotive industry, ferritic sheets hot-dip covered with AlSi coatings are often used presently [1]. Al-based protective coatings constitute the main protection against the influence of a corrosive medium at elevated temperature, including exhaust gas [2,3,4]. The tendency of Si to crystallizing from liquids in the form large and acute-angled crystals causes the risk of breaking the continuity of coatings to occur during the press forming of parts, as well as during their bonding. This urges the manufacturers to look for technological solutions for the application of coatings on finished products among the PVD techniques.The application of coatings by the PVD (Physical Vapour Deposition) method involves the deposition of a material, previously brought in a gaseous state, on a substrate. PVD techniques are currently among the most commonly used methods of producing nanocrystalline coatings of unique structural features [5]. To produce homogeneous multicomponent coatings, several discs of different materials are sputtered simultaneously in large vacuum installations. In this study, a single disc of a multi-component material was used. According to literature information, Al and Si show a different tendency to sputtering. It is estimated that aluminium sputters approx. 2 times faster than silicon [6]. Having in mind the different susceptibility of Al i Si to sputtering, as well as the varying thermal expansion of the phases (αAl and Si) [7] already in the coating, the effect of phase refining (by modification with the TiBAl refiner) in the sputtered alloys on the mechanical properties of coating was additionally determined in the study. Material and research methodologyAlSi coatings fabricated on the 1.4512 steel substrate in the magnetron sputtering technology were investigated. Sputtering discs were made from AlSi casting alloys with the sub-, peri-and hypereutectoid composition, respectively: AlSi7, AlSi11 and AlSi20. One of the coating series was fabricated from AlSi11 and AlSi20 subjected to modification with the TiBAl refiner during casting with the aim of refining the phases (αAl and Si). The chemical composition of the coatings, as determined on their surface, and coating thicknesses are given in the tabl...

Increasing the oxidation resistance of γ-TiAl by applying a magnetron sputtered aluminum and silicon based coating

“…A similar branched structure of the Si grains within the Al matrix is found in literature for Al-20Si sputtered coatings as well [50,51]. In the literature, no heating was mentioned so it is suggested that the sputtering took place at room temperature.…”