研究目的
To adjust the mismatch of coefficient of thermal expansion between NbSi2 coating and Nb alloy while suppressing the pest oxidation of NbSi2 coating at moderate temperatures.
研究成果
The Ti-Al-doped NbSi2-Si3N4 coating exhibits the best oxidation resistance at 750 °C among the four coatings. The improvement in the pest oxidation resistance can be attributed to the selective oxidation of Ti and Al in the coating.
研究不足
The study focuses on the oxidation behavior at 750 °C and the suppression of pest oxidation through doping with Ti and Al. The long-term stability and performance at higher temperatures or under different environmental conditions were not investigated.
1：Experimental Design and Method Selection:
Spark plasma sintering (SPS) process was utilized to prepare the coatings.
2：Sample Selection and Data Sources:
Commercial pure Nb sheets were used as the coating substrates. Elemental powders of Nb, Si, Ti, Al, and Si3N4 were used as the coatings’ starting materials.
3：List of Experimental Equipment and Materials:
Spark plasma sintering (SPS, Sinterland-L110), X-ray diffraction (XRD, Bruker D8), Scanning electron microscopy (SEM, SU8220), and electron-probe microanalysis (EPMA, EPMA-8050G).
4：Experimental Procedures and Operational Workflow:
The powder mixtures were weighed according to proportion and then dry-mixed in a mechanical shaker for 24 h. All coatings were sintered at 1400 °C at a heating rate of 100 K/min and a holding time of 5 min under 30 MPa in an evacuated atmosphere.
5：Data Analysis Methods:
XRD, SEM, and EPMA were utilized to analyze the microstructure and chemical compositions of the coatings.
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