Characterization of the Structure of Plasma-Sprayed Metallic Silicide Coatings(Materials, Metallurgy & Weldability)
MoSi_2 and TiSi_2 coatings are deposited by low pressure plasma spraying processes. The structures of the deposited coatings are characterized by using X-ray diffraction. The effects of annealing treatment on the structures of the coatings under vacuum and under ambient atmospheres are examined. It is found that the MoSi_2 coating is consisted of a meta-stable hexagonal MoSi_2 and a stable tetragonal MoSi_2, while TiSi_2 coating is constituted from meta-stable orthorhombic base centered phase (C49) and stable orthorhombic face-centered phase (C54). The annealing of both silicide coatings under the temperatures from 873K to 1073K leads to the phase transformation from meta-stable silicides to stable silicides. The annealing of the TiSi_2 coating at ambient atmospheres results in the oxidation of silicide and formation of TiO_2 and SiO_2, which fills up the pores in the coating and leads to densification of the coating. The annealing treatment also causes the diffusion of silicon towards the substrate from the coating to form a strong bond between coating and substrate. However, the diffusion of silicon depletes the silicon in the coating and may reduce the instability of the silicide coating.
- Transactions of JWRI
Transactions of JWRI 27(2), 47-52, 1998-12