Abstract

Titanium alloys have a thermal barrier temperature of 600℃, however, the preparation of Ti-Al-Si coating is one of the effective methods to improve the high temperature oxidation resistance of titanium alloys. Due to the preferential combination of Si and Ti, it is difficult to form a Ti-Al alloy phase layer with excellent oxidation resistance at high temperature. In order to solve this problem, the two-step hot-dipping + pre-oxidation method was creatively used to prepare Ti-Al-Si composite coatings, and a small amount of Cr was added to improve the high temperature oxidation resistance of the coatings. The phase structure of the coating was analyzed by XRD. The microstructure of the coating was characterized by SEM. EDS was used to analyze the content and distribution of elements in the coating. The results shown that the Cr-added Ti-Al-Si composite coatings were in the sequence of Ti3Al layer, TiAl layer, TiAl2 + Ti5Si3 layer, Ti(Al,Si,Cr)3 layer, L-(Al,Si) layer, and Al2O3 layer from the substrate. Cr segregated on the Ti(Al,Si,Cr)3 phase boundary, and promoted the selective oxidation of Al to form Al2O3. The dense and continuous Ti-Al binary intermetallic layer can prevent cracks from spreading to the substrate, which further improves the high temperature oxidation resistance.

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