Abstract
Research is being conducted on Mo- and Nb-based alloys that are used in the aerospace sector, including those used for advanced gas turbines and aircraft engines. There is a limit to using Mo, which has a high density among refractory metals, and a few studies exist describing the addition of Nb to Mo–silicide alloys. There is a lack of guidance research on the basic Nb:Mo ratio of alloys, and it is necessary to study how to improve oxidation resistance. Therefore, this study aims to improve oxidation resistance by controlling the ratio of Nb and Mo in (Nbx, Moy)Si2 coating layers with Si pack cementation coatings on Nb–Mo alloys. Static oxidation tests were carried out at 1200 °C for 6 h to confirm the oxidation characteristics. As a result, a SiO2 or SiO2 + Nb2O5 ceramic protective layer was formed on the surface. After the oxidation tests, alloys with a Nb content of less than 35 at.% were found to protect the surface. The ratios of Nb and Mo in the Nb–Mo alloy and silicide coating layer were compared, and the improvement of oxidation resistance is discussed in terms of microstructural evolution.
Highlights
In recent years, next-generation technology has become preoccupied with eco-friendly and economic factors, and many studies in various fields have focused on improving efficiency
The aerospace industry focuses on engine efficiency, including advanced gas turbines and aircraft engines [1,2]
Ni-based Haynes 230 and/or Inconel 718 alloys, which have been used as turbine engine materials for decades, have an operating temperature below ~1100 ◦ C [3]
Summary
Next-generation technology has become preoccupied with eco-friendly and economic factors, and many studies in various fields have focused on improving efficiency. Among the methods of improving the efficiency of an engine, much research has been conducted on increasing the operating temperatures of materials [1,2]. Ni-based Haynes 230 and/or Inconel 718 alloys, which have been used as turbine engine materials for decades, have an operating temperature below ~1100 ◦ C [3]. By reaching a service temperature of ~1300 ◦ C without a cooling system, the output power of an engine can be improved by about 50% In this regard, Mo-based alloys have been considered as alternatives [2]. Many studies have been conducted on high-temperature alloys with designs that can enhance the material properties [4,5,6,7,8].
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