Microstructure and oxidation behaviour of TiAlSi coatings on TiAlCrNb alloy

Purpose: Influence of slurry coating deposition TiAlSi with different Si concentration on oxidation resistance of Ti48Al2Cr2Nb intermetallic alloy and investigation of the influence of Si addition on the structure of obtained coatings. Design/methodology/approach: The research allowed the identification of microstructural changes that take place during oxidation test of TiAlSi coating during isothermal oxidation at 900 degrees centigrade for 500 h of exposure in air. The scope of the research encompassed a microstructural analysis with the use of macro and micro investigation - LM, SEM microscopy, XRD phases analysis and EDS analysis. Findings: The investigation has shown that the thickness of the coatings TiAlSi was in range from 30 to 40 mm. The structure of the silicon-modified aluminide coatings is as follows: the outer zone consisting of TiAl3 phase and titanium silicides/the middle zone consisting of columnar titanium silicides in phase TiAl3 matrix/the inner zone consisting of TiAl2 phase. In oxidation test, the much smaller increase of the mass has been observed, as a result of the coating deposition. The smallest mass changes have been detected in samples containing the coatings formed from 12.5% Si slurries. Research limitations/implications: The discussed research proves that main reason of much better oxidation resistance of TiAlSi coated base alloy is related to rich in aluminium TiAl3 phase presents in coating modified by Si. In addition silicon decrease activity of titanium, and in consequence the susceptibility of Al to selective oxidation is much stronger. The presents of Si due to Ti-Si phase generation with high oxidation resistance. Practical implications: The slurry method can be applied in aerospace and automotive industry as low-cost technology of producing of aluminide coatings on intermetallics. Originality/value: New method of aluminide coatings deposition on TiAl alloys.