Microstructure and oxidation resistance of Si modified aluminide coating on TiAl based alloys

Abstract

Two c-TiAl based alloys of Ti-48Al-2Nb-2Cr (at-%) and Ti-45Al-2Nb-2Mn-1B (at-%) were used as substrate materials. The coatings' deposition process was prepared using the slurry method. After the deposition of water based slurry containing Al and Si powders on the substrates, diffusion treatment has been carried out at 1000uC for 6 h in Ar atmosphere. The structure of the silicon modified aluminide coatings is as follows: (a) an outer layer consisting of a TiAl 3 matrix and Ti 7 Al 5 Si 12 grains dispersed within this matrix, (b) a middle layer composed of a TiAl 3 matrix and columnar grains of Ti 5 Si 3 and (c) an inner layer as TiAl 2 phase. According to the energy dispersive spectroscopy analysis results, it can be concluded that Cr had a high tendency to move towards the Si enriched compounds. The results of isothermal oxidation test of 1000uC/200 h showed that the formation of Si modified aluminide coatings on c-TiAl alloys by slurry method can greatly improve their high temperature oxidation resistance.

Oxidation Behavior of Al-Y Coating on γ-TiAl at 900°C

“…Furthermore, ceramic coatings were used in TiAl alloy to improve the property of oxidation resistance. Such as Cr 2 O 3 and Al 2 O 3 , which have been used to enhance the long time steady application in high temperature environment [16][17][18][19][20][21][22]. Nevertheless, smash and fragmentation of ceramic coatings cannot be averted because of the diffusion and lose of salutary elements in high temperature environment [23][24][25].…”

Critical Raw Materials Saving by Protective Coatings under Extreme Conditions: A Review of Last Trends in Alloys and Coatings for Aerospace Engine Applications

“…Fabrication of Si-Al, Al-Y, and Si-Al-Y layers on TiAl alloys have been shown to produce a series of different intermetallic layers (e.g., aluminide and silicide) and oxide layers, increasing the oxidation resistance of the coated alloys [227][228][229][230][231][232]. In particular, J. Xiang et al [232] Platinum aluminide coatings seem to protect the titanium alloys from oxidation as well as from hot corrosion, preventing the formation of the alpha phase.…”

“…They observed an excellent oxidation resistance of the Ti alloys up to 800 • C, thanks to Pt, which effectively promotes continuous alumina scale formation during high temperature exposure. Fabrication of Si-Al, Al-Y, and Si-Al-Y layers on TiAl alloys have been shown to produce a series of different intermetallic layers (e.g., aluminide and silicide) and oxide layers, increasing the oxidation resistance of the coated alloys [227][228][229][230][231][232]. In particular, J. Xiang et al [232] coated a Ti alloy by means of Si-Y co-deposition and aluminization, which, due to inward diffusion of Al atoms and outward diffusion of Ti and Nb atoms, gave rise to the formation of different mixed intermetallic layers and promoted the preferential development of Al2O3 on the surface in spite of the less resistant TiO2 oxide.…”

Microstructural investigation of the coatings prepared by simultaneous aluminizing and siliconizing process on γ-TiAl

“…Several researchers have prepared aluminide coatings on -TiAl alloy [6,[30][31][32][33]. The Si-modified aluminide coatings are also prepared on -TiAl alloys by pack cementation method to form titanium silicide layers on them.…”

“…Gamma TiAl intermetallic compound is a low density material, which has been widely used for its high specific strength, good oxidation and creep resistance at fairly high temperatures [1][2][3][4][5]. These attractive properties make the material work in the aerospace and automotive industry as well as use in manufacture of low-pressure turbine blades [4][5][6][7][8][9]. But this alloy is not sufficient oxidation protection above 800 o C [10,11].…”