Influence Mechanism of Silicon on Carbide Phase Precipitation of a Corrosion Resistance Nickel Based Superalloy

Abstract

The effect of silicon on diffusion behavior of the carbide forming elements in Ni-Mo-Cr-Fe based corrosion-resistant alloy is studied by diffusion couple experiment. One group of diffusion couples are made of the alloy with a different silicon content, another group of diffusion couples are made of pure nickel and the alloy with different silicon content (0Si, 2Si). Two groups of alloys with same silicon content and different carbon content are also prepared, the microstructure of solution and aging state of these two groups alloys are analyzed, and their stress rupture properties are tested. The effect of silicon on the diffusion of alloy elements and the interaction effect of carbon and silicon on the microstructure and stress rupture properties of the alloy are analyzed. The mechanism of Si on the precipitation behavior of carbide phase in Ni-Mo-Cr-Fe corrosion resistant alloy is discussed. The results show that silicon can promote the diffusion of carbide forming elements and the formation of carbide. The precipitation behavior of the secondary phase is the result of the interaction effect of silicon and carbon, and is related to the thermal history of the alloy. Combined with the characteristic of primary carbides, it is confirmed that the precipitation of M12C type secondary carbide is caused by the relative lack of carbon element and the relative enrichment of carbide forming elements such as molybdenum. The stress rupture properties of two silicon-containing alloys with different carbon contents in solution and aging state are tested. The stress rupture life of low carbon alloy is lower compared with high carbon alloy at solution state, but after aging treatment, the stress rupture life of low carbon alloy is significantly improved, and higher than that of high carbon alloy. The main aim of this research is to reveal the influence mechanism of silicon on carbide phase precipitation of a Ni-Mo-Cr-Fe based corrosion-resistant superalloy, which provides theoretical basis and reference for later alloy design and engineering application.

Assessing the interfacial corrosion mechanism of Inconel 617 in chloride molten salt corrosion using multi-modal advanced characterization techniques

“…Previous investigations have reported the formation of intergranular Si-Mo-enriched M 6 C carbides in heat-treated Ni-Mo-Cr superalloys (Xu et al, 2015;Liu et al, 2020). Si has been reported to promote the diffusion of elements and reduce C to form carbides precipitates near grain boundaries (Liu et al, 2020). It is noteworthy to mention that TEM EDS analysis in this investigation did indicate slight C enrichment in the Mo 3 Si 5 (Figure 8) and Crenriched precipitates (Supplementary Figure S2), but no conclusive evidence is able to discern elucidation of a corrosion-induced Si-Moenriched M 6 C carbide or Cr-based carbide, respectively.…”

“…Intergranular Mo-enriched precipitates were observed in as-received Alloy 617 in this investigation, Supplementary Figure S1. Previous investigations have reported the formation of intergranular Si-Mo-enriched M 6 C carbides in heat-treated Ni-Mo-Cr superalloys (Xu et al, 2015;Liu et al, 2020). Si has been reported to promote the diffusion of elements and reduce C to form carbides precipitates near grain boundaries (Liu et al, 2020).…”

Strengthening Mechanisms in Nickel-Copper Alloys: A Review

“…Ni can dissolve high concentrations of alloying elements compared to other metals [34]. Alloying elements increase mechanical strength via solid solution [35][36][37][38][39][40] or precipitation strengthening [41][42][43][44][45]. However, the solid solution strengthening effect of Cu is much lower compared to other elements [19,46].…”