Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
7988230 | Intermetallics | 2018 | 10 Pages |
Abstract
Mo-Ti-Si based materials are promising candidates for high-temperature applications beyond the capability limits of nickel based superalloys. In the present investigation, two alloy compositions with different Si content namely Mo-40Ti-30Si (in at.%) (alloy 1) and Mo-40Ti-10Si (alloy 2) were prepared in the form of plates by adopting mechanical alloying and subsequent reactive hot pressing at 1600â¯Â°C. The densities of the alloys were found to be much lower than the conventional alloys used for high-temperature applications. The detailed microstructural characterization using scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and electron back-scattered diffraction (EBSD) analysis indicated that alloy 1 was composed with Ti(Mo)5Si3 matrix and Ti(Mo)3Si precipitates. Alloy 2 consisted with three phase microstructure containing α-Mo(Ti)ss, β-Ti(Mo)ss and Mo(Ti)3Si. Micro-hardness values of 1400â¯Hâ¯V and 850â¯Hâ¯V respectively for alloy 1 and alloy 2 were noticed, however, alloy 1 showed the tendencies of micro-crack formation from the corners of the Vickers indentations. Alloy 1 showed a superior isothermal oxidation resistance at 900â¯Â°C, 1000â¯Â°C, and 1300â¯Â°C for prolonged duration due to formation of a thin duplex SiO2 (TiO2) oxide scale. However, the formation of a porous oxide layer led to evaporation of MoO3, showing drastic weight loss of alloy 2â¯at all three tested temperatures. Enrichment of Si was done using pack siliconizing process forming a (Mo, Ti)Si2 layer of thickness 10â¯Î¼m and 30â¯Î¼m on the surfaces of alloys 1 and 2 respectively at 900â¯Â°C. The silicide coated alloy 1 showed further improvement in the oxidation behaviour, and enrichment of Si on alloy 2 surface imparted a drastic improvement in the resistance against oxidation in air at 1300â¯Â°C for the prolonged exposure times of 70â¯h.
Related Topics
Physical Sciences and Engineering
Materials Science
Metals and Alloys
Authors
Sanjib Majumdar, Bhaskar Paul, Pankaj Kumar Singh, Jugal Kishor, Vivekanand Kain,