This paper compares the abrasibility of aluminium-silicon coatings with silicon crystals of various forms. The tests were performed on Al-Si coatings with the chemical comp67890-osition corresponding to that of hypoeutectic and peritectic silumins (6-10wt% Si), manufactured by hot-dipping on type X2CrTi12 steel and by cold cladding with 60% cold reduction on AlMn1Cu alloy. The hot-dip coatings deposited on X2CrTi12 steel were investigated as made and after a two-stage heat treatment: 420oC/2h/water and 120oC/2h/air. The morphology, shape, and size of silicon crystals in the coatings were studied under a microscope and with the image analysis technique (determining the shape factor among other parameters). Image analysis was also applied to the evaluation of abrasive wear resistance of the coatings using a ball wear test. Their adhesion strength was tested with the scratch test method. The test results indicated that the change in Al-Si coating silicon crystal morphology (from large sharp edged and needle-like to smaller rounded particles) was heat induced, which, compared to the pre-treatment condition, lowered abrasion resistance values and produced a more uniform abrasion loss. This condition was regarded as more desirable in terms of maintaining the coating continuity during drawing, with no risk of spalling. It was also demonstrated that clad Al-Si coatings could provide an alternative solution for the widely used hot dip coatings on steel sheet.

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...

Exhaust systems are susceptible to in-service wear because of their exposition to the very aggressive corrosive environment. Various stainless steels grades (mostly ferritic and austenitic, but also martensitic and duplex) and protective coatings are currently used for exhaust system elements to increase their aestetics and corrosion resistance. This article focuses on evaluation and comparison of the common corrosion properties of two stainless steels with different microstructures (ferritic and austenitic) used for exhaust system components at the low ambient temperature (35 °C). An aggressive acidic corrosion solution for electrochemical cyclic potentiodynamic tests (ASTM G61) was chosen to simulate partly inner (condensate) and also external environment (reaction of exhaust gases with water, chlorides in solution after winter road maintenance). Exposure tests of the pitting corrosion resistance were performed according to ASTM G48 standard method.

No abstract