Microstructural evolution and oxidation behaviour of Mo-Si-B coatings on an Nb-16Si-22Ti-7Cr-2Al-2Hf alloy at 1250 °C prepared by spark plasma sintering

• Published in: Surface & coatings technology Vol. 352; pp. 320 - 329
• Main Authors: Wen, S.H., Zhou, C.G., Sha, J.B.
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 25.10.2018; Elsevier BV
• Subjects: Diffusion coatings; Diffusion layers; Diffusion rate; Intermetallic compounds; Intermetallics; Metal coatings; Microstructural evolution; Microstructure; Molybdenum disilicides; Niobium base alloys; Oxidation; Oxidation resistance; Plasma sintering; Protective coatings; Reaction kinetics; Silicon dioxide; Spark plasma sintering; Time dependence; Metal coatings; Intermetallics; Spark plasma sintering; Microstructural evolution; Oxidation
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/j.surfcoat.2018.08.027

Mo-Si-(5, 10, 15)B ternary coatings were firstly coated on an Nb-Si based alloy using the spark plasma sintering technique. The Mo-Si-B coatings consisted of an outer MoSi2/MoB/SiO2/Mo2B5 (Mo5Si3) layer and an inter-diffusion zone, while SiO2 was formed during SPS. The oxidation kinetics curves exhibited parabolic time dependence and 5B coating had the lowest mass gain of approximately 0.41 mg/cm2 after oxidation at 1250 °C for 100 h. The good oxidation resistance results from a dense and protective borosilicate layer formed on coatings and the low growth rate of the inter-diffusion zone beneath the Mo-Si-B coatings. [Display omitted] •SPSed Mo-Si-B coatings on Nb-Si substrate have an outer and an inter-diffusion layers.•Oxidation kinetics of the coatings obeys the parabolic law.•Mo-62Si-5B coating has the lowest mass gain oxidized at 1250 °C.•Good oxidation resistance results from a dense borosilicate layer.•Growth rate of inter-diffusion layer is dominated by diffusion of Si.