Preparation And Oxidation Behavior Of Mo-Si-B Coating On Nb-Ti-Si Alloy

Nb-Ti-Si alloy is an important high-temperature structural material, owing to its high melting point, excellent high temperature mechanical properties and other characteristics. Alloying makes its oxidation resistance activity to some extent improve, but it still needs to prepare oxidation resistance coating on the surface to meet the requirements of high temperature under aerobic conditions. In this paper, Mo-Si-B coating was prepared on the surface of Nb-Ti-Si alloy to improve its high-temperature oxidation resistance.Firstly, the Mo coating was prepared on the surface of Nb-Ti-Si alloy by glow plasma deposition. The influence of deposition temperature and time on Mo coating thickness, morphology, as well as the interfacial bonding, were studied. Following the deposition of Mo coating on the substrate, the Mo-Si-B coating was prepared through pack Si-B co-deposition process. The morphology and the structure of the Mo-Si-B coating were studied. In order to detect the oxidation resistance of the Mo-Si-B coating, it was oxidized at 600℃ and 1250℃ in air, respectively. The scale and the coating morphology were studied after oxidation. XRD, SEM, BSE, EDS and WDS techniques were used to analysis the coating in this study. Come to the following.(1) The Mo coating prepared by glow plasma deposition became more thicker with the deposition time prolonging. With the deposition temperature rise, the Mo layer became more denser and the thickness of the interdiffusion zone at the interface of the Mo coating and the substrate became more thicker.(2) The Mo-Si-B coating prepared by pack Si-B co-deposition on the Mo coating has multi-layer structure.(3) The oxides SiO2 and B2O3 formed on the surface of the Mo-Si-B coating after 600℃ oxidation. There were also Al2O3 residues from the pack on the surface. After oxidation, the coating structure was nearly unchanged.(4) After 1250℃ oxidation for 5h and 20 h, continuous and dense oxide film is formed on the surface of the Mo-Si-B coating. It mainly consisted of SiO2 and some Nb2O5, TiO2. After oxidation at 1250℃, NbSi2 layer was degraded into Nb5Si3 and cracks generated at the interface of MoSi2/NbSi2 layers.