Publication: Modified slurry molybdenum silicide coating of ni-based alloy for high temperature application
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Date
2024-08-01
Authors
Lim Kuan Heng
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Abstract
This study focuses on the development and characterization of modified slurry molybdenum silicide coatings for Ni-based alloy (Inconel 625) substrates which will be utilized in high temperature application. Mo-Si-B coatings were investigated as possible protective layers to increase Inconel 625's resistance to high-temperature oxidation. Mo-Si-B coatings with three distinct compositions were applied by brushing and sintered at temperatures between 1000°C and 1200°C. X-ray diffraction (XRD), elemental mapping, cross-sectional micrographs, and surface morphology analysis were among the characterisation techniques used in the study.
The findings showed that more homogeneous microstructures with lower porosity were developed by raising the sintering temperature and reducing the boron element in the Mo-Si-B coating. The SEM cross-sectional analysis of three Mo-Si-B coating compositions revealed the distribution of elements across the coating and substrate layers. Molybdenum forms the matrix for the coating, while silicon and oxygen are distributed uniformly throughout the coating layers.
The presence of several phases, such as borides and silicides, which differ based on the coating composition and sintering temperature, was verified by XRD analysis. At 1000°C, the 62.5Mo-12.5Si-25B coating had α-Mo and Mo2B peaks, whereas the 76Mo-10Si-14B coating displayed phases of Ni3Si and MoNi4. Stable phases including Mo5SiB2 and MoSi3 formed at 1200°C, which improved the coating's densification and decreased its porosity. 80 Mo-10Si-10B coating sintered at 1200oC for 1 hour reveals the most promising coating layer by the formation of the α-Mo, Mo5SiB2, Mo3Si phases within the coating.