MoSi&lt;sub&gt;2&lt;/sub&gt; Composites for High Temperature Structural Applications

Mo–Si–B and Mo–Hf–Si–B coatings were produced by magnetron sputtering of a MoSiB ceramic target equipped with 2 or 4 Hf segments. Their structure and composition were studied by scanning electron microscopy, energy dispersive spectro scopy, X-ray diffraction analysis, and Raman spectroscopy. Mechanical properties were determined by nanoindentation at a load of 4 N. The crack resistance of coatings was studied on a microhardness tester at loads of 0.25–1.0 N. The oxidation kinetics was studied at 1000 °C in air with a total exposure of 300 min. The heat resistance of coatings was determined as a result of short-term annealing at 1500 °C. Electrochemical tests were carried out by voltammetry in the 1N H2SO4 solution. The results showed that the Mo–Si–B coating and Mo–Hf–Si–B coating obtained using 2 Hf segments feature by a columnar structure. The use of 4Hf segments in coating deposition led to an increase in density and suppression of the undesirable columnar structure formation. It was shown that hafnium introduction into the coating composition increases the growth rate by 20% and reduces the grain size of the main component of the h-MoSi2 phase by an order of magnitude, while simultaneously promoting HfB2 formation. Maximum hardness (27 GPa), Young’s modulus (370 GPa) and elastic recovery (62 %) were achieved for the Mo-Si-B coating. The hardness of coatings obtained using 2 and 4 Hf segments decreases by 1.9 and 1.6 times, respectively. During the Mo–Si–B and Mo–Hf–Si–B (2Hf) coating microindentation, radial cracking was observed. The sample obtained with the maximum concentration of hafnium featured by the best crack resistance. Electrochemical tests showed that the corrosion resistance of coatings increases in the Mo–Hf–Si–B (2Hf) → Mo–Si–B → Mo–Hf–Si–B (4Hf) series. All coatings showed good oxidation resistance at 1000 and 1500 °C. However, coating delamination areas were observed on the surface of Mo–Si–B and Mo–Hf–Si–B (2Hf) samples. The Mo–Hf–Si–B (4Hf) coating showed a lower oxide layer thickness and better oxidation resistance due to the dense SiO2 + HfOх protective layer formation.

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MoSi<sub>2</sub> Composites for High Temperature Structural Applications

Abstract: In this paper, the basic limitations of superalloys’ in high temperature performances will be explained and then after giving the important properties of MoSi2, some interesting composites of this material will be discussed as a candidate structural material for gas turbine engines.

Cited by 3 publications

References 19 publications

Effect of Substrate and Annealing Ambient on the Conductivity of Sputtered MoSi2 Ceramic Thin Film

Effect of Substrate and Annealing Ambient on the Conductivity of Sputtered MoSi2 Ceramic Thin Film

Oxidation resistance of Cr-modified MoSi2 composites at high temperature

Structure and properties of Mo–Hf–Si–B coatings obtained by magnetron sputtering using MoSiB/Hf mosaic target

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