(1. 南昌航空大學(xué) 材料科學(xué)與工程學(xué)院，南昌 330063； 2. 南京航空航天大學(xué) 材料科學(xué)與技術(shù)學(xué)院，南京 210016)
摘 要: 采用機(jī)械活金化+熱壓燒結(jié)法制備5種不同相組成的Cr-Nb合金，研究相組成對Cr-Nb合金在950~1 200 ℃空氣中氧化行為的影響。結(jié)果表明，Cr相能顯著增加NbCr2合金950 ℃的抗氧化性能；而Nb相不利于合金高溫抗氧化性的提高，甚至發(fā)生災(zāi)難性氧化。SEM和XRD分析顯示，單相Cr-2.5Nb合金發(fā)生了Cr的外氧化，只形成單一的Cr2O3膜；而雙相Cr-18.5Nb合金和單相Laves相NbCr2合金均發(fā)生Cr的外氧化和內(nèi)氧化，形成兩層結(jié)構(gòu)的氧化膜。但隨著氧化溫度增加到1200℃，由于Cr2O3的揮發(fā)，導(dǎo)致Cr-Nb合金高溫抗氧化性變差。因此，為滿足實(shí)際高溫應(yīng)用要求，對富軟第二相Cr或Nb的NbCr2基合金實(shí)施相應(yīng)的表面防護(hù)是必須的。
關(guān)鍵字: Cr-Nb合金；Laves相；軟第二相；相組成；氧化行為
（1. School of Materials Science and Engineering, Nanchang Hangkong University, Nanchang 330063, China; 2. College of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China）
Abstract:Five types of Cr-Nb alloys with different phase constitutions were fabricated by mechanical alloying and hot pressing. The influence of phase constitution on the oxidation behavior of the hot pressed Cr-Nb alloys were investigated at 950−1 200 ℃ in air. The results show that Cr phase improves the oxidation resistance of Laves phase NbCr2 based compounds at 950 ℃. However, Nb phase deteriorated the oxidation resistance, moreover, Nb phase results in a catastrophic failure during oxidation. SEM and XRD analyses indicate that the CrSS phase (Cr-2.5Nb) exhibits selective Cr oxidation and forms a continuous chromia scale. However, single phase alloys of Cr-33Nb and two phase alloys of Cr-18.5Nb exhibit that internal and external oxidation happen simultaneously for the active element chromium, and their oxide scales are made with a multi-layered scale consisting of an outer layer being a porous, loosely adherent Cr2O3 layer and the inner layer being of CrNbO4. With the exposure temperature increasing up to 1 200 ℃, the oxidation resistance of Cr-rich Cr-Nb alloys decreases due to the continuous vaporization of CrO3 in the oxide scale. Therefore, it is necessary to apply surface protective coatings on Cr(or Nb)-NbCr2 alloys to promote their application in the high temperature environment.
Key words: Cr-Nb alloys; Laves phase; ductile phase; phase composition; oxidation behavior
