Silicon and chromium depletion during the long-term oxidation of thin-sectioned austenitic steel

被引:42
作者
Evans, HE
Donaldson, AT
机构
[1] Univ Birmingham, Sch Met & Mat, Birmingham B15 2TT, W Midlands, England
[2] BNFL Magnox Generat, Berkeley Ctr, Berkeley GL13 9PB, Glos, England
来源
OXIDATION OF METALS | 1998年 / 50卷 / 5-6期
关键词
austenitic steel; oxidation; finite thickness samples; chromium and silicon depletion; EPMA measurements;
D O I
10.1023/A:1018808925756
中图分类号
TF [冶金工业];
学科分类号
0806 ;
摘要
Electron-probe microanalysis (EPMA) measurements are reported of the residual silicon and chromium concentrations in thin sections (0.38 mm) of a 20Cr-25Ni-Nb-stabilized austenitic steel oxidized in a CO2/1%CO environment for maximum periods of around 40,000 hl at temperatures in the range 900 to 950 degrees C. The depletion profiles obtained have been analyzed using the theoretical treatment of Whittle and Cowen-Webster. It is found that silicon depletion occurs slowly because of the low rate of thickening of the silica interlayer formed below the much-thicker, chromia-surface layer. This, coupled with relatively rapid diffusion within the steel, leads to a flat depletion profile. By contrast, the more rapid oxidation of chromium develops large concentration gradients of that element in the alloy in the vicinity of the oxide-metal interface. In each case, the solute concentration at this interface was very much larger than that for equilibrium with the respective oxide, indicating that the oxidation kinetics were determined by transport within the oxide layer rather than in the steel. In all the examples studied, the theoretical analysis produced good agreement with the depletion measurements using oxidation rate constants consistent with the metallographic measurements and diffusion coefficients of similar value to those reported in the literature.
引用
收藏
页码:457 / 475
页数:19
相关论文
共 17 条
  • [1] ALLOY DEPLETION PROFILES RESULTING FROM PREFERENTIAL REMOVAL OF LESS NOBLE-METAL DURING ALLOY OXIDATION
    BASTOW, BD
    WHITTLE, DP
    WOOD, GC
    [J]. OXIDATION OF METALS, 1978, 12 (05): : 413 - 438
  • [2] BENNETT MJ, 1984, OXID MET, V24, P473
  • [3] Bohnenkamp K., 1964, ARCH EISENHUT TENWES, V35, P1011, DOI [10.1002/srin.196401702, DOI 10.1002/SRIN.196401702]
  • [4] Cowen H. C., 1974, CORROSION STEELS CO2, P349
  • [5] Ericsson T., 1970, Oxid. Met, V2, P401, DOI [10.1007/BF00604478, DOI 10.1007/BF00604478]
  • [6] INFLUENCE OF A TITANIUM NITRIDE DISPERSION ON THE OXIDATION BEHAVIOR OF 20-PERCENT-CR-25-PERCENT-NI STAINLESS-STEEL
    EVANS, HE
    HILTON, DA
    HOLM, RA
    WEBSTER, SJ
    [J]. OXIDATION OF METALS, 1978, 12 (06): : 473 - 485
  • [7] EVANS HE, 1995, INT MATER REV, V40, P1, DOI 10.1179/095066095790151124
  • [8] EVANS HE, 1988, MATER SCI TECH SER, V4, P415, DOI 10.1179/026708388790331474
  • [9] CHROMIUM-DEPLETED ZONES AND OXIDATION PROCESS IN STAINLESS-STEELS
    EVANS, HE
    HILTON, DA
    HOLM, RA
    [J]. OXIDATION OF METALS, 1976, 10 (03): : 149 - 161
  • [10] EVANS HE, 1988, MATER SCI TECH SER, V4, P1089, DOI 10.1179/026708388790221278