应用d—电子合金设计理论发展新型抗热腐蚀单晶镍基高温合金——Ⅱ合金元素对显微组织和性能的影响

APPLICATION OF d-ELECTRON ALLOY DESIGN THEORY TO DEVELOPMENT OF HOT CORROSION RESISTANT Ni-BASE SINGLE CRYSTAL SUPERALLOYS——Ⅱ. Effects of Refractory Metals Ti, Ta and Nb on Microstructure and Properties

本文系统地研究了Ti,Ta和Nb三个γ′形成元素在抗热腐蚀合金系统Ni-16Cr—9Al-4Co—2W—1Mo—Ti-Ta—Nb(at-％)中的作用该合金系统是根据d-电子合金设计理论和镍基高温合金合金化的特点选出的根据DTA和图象仪分析结果确定了凝固反应温度以及共晶(γ+γ′)体积分数在Ti-Ta—Nb浓度三角形中的等值线分布,与参考合金IN738LC相比较,在所研究的大部分成分范围内,设计合金表现出很低的共晶(γ+γ′)析出(<0.4v-％),较低的凝固范围(<65℃)和较宽的热处理温度范围(>100℃),说明合金具有良好的组织稳定性,单晶铸造性能和热处理工艺性能.经长期时效(900℃/500h)后,无TCP相析出,在很宽的成分范围内,试验合金表现出良好的抗热腐蚀性能(900℃/24h坩埚试验,失重<20mg/cm^2)综合各项结果。

A study was conducted of the effects of refractory metals Ti, Ta and Nb on themicrostructures and properties of a hot corrosion resistant alloy system Ni-16Cr-9Al- 4Co-2W-1Mo-(0-4)Ti-(0-4)Nb, in at.-%, which was selected based on the d-elec-trons alloy design theory and some basic considerations of an alloying features of single crys-tal Ni-base superalloys. The contour lines of solidification reaction temperatures and eutectic(γ+γ′) volume fraction in the Ti-Ta-Nb compositional triangle were determined by DTA andimaging analyzer. Compared with the reference alloy IN738LC, in most of the compositionalranges studied, the designed alloys show very low amount of eutectic (γ+γ′), ≤0.4 v.-%, low-er solidification range, ≤65℃, and wider "heat treatment window", >100℃, which indi-cates that the alloys should have the promising microstructural stability, single crystalcastability and be easier for complete solution treatment. In wide compositional ranges, thedesigned alloys showed good hot corrosion resistance (mass loss less than 20 mg / cm^2 after24 h kept in moiten salt at 900℃). By summarizing the results, the promising alloy,compositional ranges with balanced propertise were determined for the final alloy design step,i.e., the single crystal growth and mechanical property characterization of the alloys selectedfrom the above regions.