【摘要】 采用机械活金化+热压烧结法制备5种不同相组成的Cr-Nb合金,研究相组成对Cr-Nb合金在950～1200℃空气中氧化行为的影响。结果表明,Cr相能显著增加NbCr2合金950℃的抗氧化性能;而Nb相不利于合金高温抗氧化性的提高,甚至发生灾难性氧化。SEM和XRD分析显示,单相Cr-2.5Nb合金发生了Cr的外氧化,只形成单一的Cr2O3膜;而双相Cr-18.5Nb合金和单相Laves相NbCr2合金均发生Cr的外氧化和内氧化,形成两层结构的氧化膜。但随着氧化温度增加到1200℃,由于Cr2O3的挥发,导致Cr-Nb合金高温抗氧化性变差。因此,为满足实际高温应用要求,对富软第二相Cr或Nb的NbCr2基合金实施相应的表面防护是必须的。更多还原

【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.更多还原