Fabrication and Oxidation Resistance of TiAl Matrix Coatings Reinforced with Silicide Precipitates Produced by Heat Treatment of Warm Sprayed Coatings

Abstract

Ti-Al-based intermetallics are promising candidates as coating materials for thermal protection systems in aerospace vehicles; they can operate just below the temperatures where ceramics are commonly used, and their main advantage is the fact that they are lighter than most other alloys, such as MCrAlY. Therefore, Ti-Al-Si alloy coatings with five compositions were manufactured by spraying pure Ti and Al-12 wt.% Si powders using warm spray process. Two-stage hot pressing at 600 and 1000°C was applied to the deposits in order to obtain titanium aluminide intermetallic phases. The microstructure, chemical composition, and phase composition of the asdeposited and hot-pressed coatings were investigated using SEM, EDS, and XRD. Applying of hot pressing enabled the formation of dense coatings with porosity around 0.5% and hard Ti 5 (Si,Al) 3 silicide precipitates. It was found that the Ti 5 (Si,Al) 3 silicides existed in two types of morphologies, i.e., as large particles connected together and as small isolated particles dispersed in the matrix. Furthermore, the produced coatings exhibited good isothermal and cyclic oxidation resistance at a temperature of 750°C for 100 h.

Comparison of Microstructure, Microhardness, Fracture Toughness, and Abrasive Wear of WC-17Co Coatings Formed in Various Spraying Ways

“…A warm spraying (WS) process, as a new kind of thermal spraying technology, has been used to prepare metal (e.g., Al, Cu, and Ti etc) [21][22][23], Ti6Al4V [24], hydroxyapatite (HA) [25], HA/Ti [26], Ti-Al-based intermetallic coatings [27]. Meanwhile, due to the high particle temperature, which is nevertheless lower than the melting point characteristic of standard WS processes, WC-based cermet coatings were successfully deposited by warm spraying [28][29][30][31][32].…”

PREPARATION OF NiAl-FeSi COMPOSITES BY POWDER METALLURGY

“…However, the feasibility of this substitution is limited by low fracture toughness of Ti-Al-Si materials, anisotropy of the thermal expansion coefficient of Ti5Si3 phase [6] and also by the fact that titanium was newly listed as a critical raw material in 2020 [1]. There were also other researches dealing with intermetallic composites running, such as aluminide -ceramics [7][8][9] or silicideceramics [10,11] or silicide-aluminide coatings [12][13][14].…”