Microstructure and High-Temperature Oxidation Behavior of Dy-Doped Nb–Si-Based Alloys

Abstract

Microstructures and oxidation behaviors of four Dy-doped Nb-Si-based alloys at 1250°C were investigated. The nominal compositions of the four alloys are Nb-15Si-24Ti-4Cr-2Al-2Hf-xDy (at.%), where x = 0, 0.05, 0.10 and 0.15, respectively. Results showed that the four alloys all consisted of Nbss, aNb 5 Si 3 and cNb 5 Si 3 , and the addition of Dy produced no obvious effect on the phase constitution and the microstructures of Nb-Si-based alloys. After oxidation at 1250°C for 58 h, it was found that the addition of Dy accelerated the oxidation rate of Nb-Si-based alloys and caused a larger weight gain, accompanied by the formation of a more porous and less protective oxide scale. The oxides of Nb 2 O 5 , Ti 2 Nb 10 O 29 , TiNb 2 O 7 , Ti 0.4 Cr 0.3 Nb 0.3 O 2 and glassy SiO 2 were formed on Dy-doped Nb-Si-based alloys. The hightemperature oxidation mechanism of Dy-doped Nb-Si-based alloys was discussed.

The Oxidation Resistance of Nb-Si-Based Alloys at Intermediate and High Temperatures

“…A similar compact oxide scale is observed in Nb-Si-based alloys containing high levels of Al and Cr [22]. Small additions of rare earth elements can significantly enhance the oxidation resistance of metals as well as coatings [23][24][25]. An appropriate amount of Y (0.3 at.…”

“…%) can refine alloys' microstructure and enhance oxidation resistance [23]. However, the addition of Dy accelerates the oxidation rate of Nb-Si-based alloys and causes increased weight gain [24].…”

Solid-State Diffusion Bonding of NbSS/Nb5Si3 Composite Using Ni/Al and Ti/Al Nanolayers

“…Sha et al [12] studied the toughening and strengthening behaviour of Nb-8Si-20Ti-6Hf- (6,10,14) Cr alloys prepared by the arc melting method, and the results revealed that the fracture toughness was decreased by the addition of Cr. As demonstrated by Guo et al [13], the addition of Dy had no obvious effect on phase constitution and microstructures of Nb-Si-based alloy but could significantly accelerate the parabolic oxidation rate. Kim et al [14] reported the tensile Available online at http://link.sprin ger.com/journ al/40195 properties and fracture behaviour of Nb SS /Nb 5 Si 3 alloy with the nominal composition of Nb-18Si-5Mo-5Hf-2C, in which the ultimate tensile strength (UTS) was about 310 MPa at ambient temperature and the highest UTS of 460 MPa at 1470 K.…”

A more defective substrate leads to a less defective passive layer: Enhancing the mechanical strength, corrosion resistance and anti-inflammatory response of the low-modulus Ti-45Nb alloy by grain refinement

“…Therefore, the surface layer on NbOy is thinner than that on TiOx. The difference can be explained by the Ellingham-Richardson diagram [44]. Specifically, the standard free energy change (ΔG ϴ ) of oxide formation is negatively correlated with the stability of the compound.…”