粉末冶金Ag-Cr合金在纯氧气中的氧化

Oxidation of Ag-Cr alloys prepared by powder metallurgy in 0.1 MPa O_2

研究了粉末冶金 Ag-35Cr(PM Ag-35Cr)和Ag-69Cr(PM Ag-69Cr)合金在700-800℃及0.1 MPa纯氧气中的氧化.PM Ag-35Cr合金在700-800℃纯氧气中氧化形成了复杂的氧化膜,包括Cr2O3、复合氧化物AgCrO2及其下面铬的内氧化区.PM Ag-69Cr合金形成了双层氧化膜,外层为复合氧化物AgCrO2,内层为Cr2O3,铬的内氧化被完全抑制.PM Ag-Cr合金在氧化过程中,铬向外的扩散受到合金中的两相及铬粒子颗粒较粗大等因素的限制,致使铬含量高达69％(质量分数,下同)时,合金氧化后也没有形成单一的Cr2O3外氧化膜.合金内氧化引起的体积膨胀导致在内氧化区出现压应力,使得PM Ag-35Cr合金氧化膜最外层出现了纯银.

The oxidation behavior of powder metallurgical Ag-Cr alloys at 700-800°C in 0.1 MPa O2 was studied. PM Ag-35Cr alloy formed complex scale including silver metal, Cr2O3, AgCrO2 and internal oxidation zone of chromium. A continuous layer of Cr2O3 under an external layer of AgCrO2 formed on the PM Ag-69Cr alloy. The internal oxidation of chromium was suppressed in this alloy. The oxidation of PM Ag-Cr alloys was strongly affected by the restriction to chromium diffusion due to the presence of two phases and by the relatively large size of the chromium particles, which restrained the formation of exclusive Cr2O3 scales which restrained the formation of exclusive Cr2O3 scales at the chromium contents 69%. The appearance of pure silver on the PM Ag-35Cr alloy was a result of the stress resulting from large volume change caused by internal oxidation.