Abstract
Traditional refractory materials such as nickel-based superalloys have been gradually unable to meet the performance requirements of advanced materials. The Mo-Si-based alloy, as a new type of high temperature structural material, has entered the vision of researchers due to its charming high temperature performance characteristics. However, its easy oxidation and even “pesting oxidation” at medium temperatures limit its further applications. In order to solve this problem, researchers have conducted large numbers of experiments and made breakthrough achievements. Based on these research results, the effects of rare earth elements like La, Hf, Ce and Y on the microstructure and oxidation behavior of Mo-Si-based alloys were systematically reviewed in the current work. Meanwhile, this paper also provided an analysis about the strengthening mechanism of rare earth elements on the oxidation behavior for Mo-Si-based alloys after discussing the oxidation process. It is shown that adding rare earth elements, on the one hand, can optimize the microstructure of the alloy, thus promoting the rapid formation of protective SiO2 scale. On the other hand, it can act as a diffusion barrier by producing stable rare earth oxides or additional protective films, which significantly enhances the oxidation resistance of the alloy. Furthermore, the research focus about the oxidation protection of Mo-Si-based alloys in the future was prospected to expand the application field.
Highlights
As the world population increases, the problem of global resource shortage has become increasingly prominent
A large number of studies have pointed out that Mo-Si-based alloys have outstanding high temperature performance characteristics, such as moderate density, strong electrical and thermal conductivity, ultra-high melting point, high thermal impact resistance, etc., which have been widely used in various industries [10,11]
This paper reviewed the role of rare earth elements on the oxidation behavior of Mo-Si-based alloys, and summarized the strengthening mechanism of various rare earth elements
Summary
As the world population increases, the problem of global resource shortage has become increasingly prominent. A large number of studies have pointed out that Mo-Si-based alloys have outstanding high temperature performance characteristics, such as moderate density, strong electrical and thermal conductivity, ultra-high melting point, high thermal impact resistance, etc., which have been widely used in various industries [10,11] These alloys have some inherent defects that limit their generalization as structural materials [12,13,14]. Mo5Si3-based alloys have relatively strong creep resistance, they generally present an accelerated oxidation or “pesting oxidation” phenomenon below 1000 ◦C, which is a thorny problem [15,16,17,18,19] To overcome these shortcomings, relevant research work has not stopped since the end of the 20th century [20,21,22,23,24,25]. This paper comprehensively and systematically reviewed the actions of rare earth elements such as La, Hf, Ce and Y on the antioxidant properties of Mo-Si-based alloys, especially the Mo-Si-B system, and summarized the relevant strengthening mechanisms
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