HIGH-TEMPERATURE CREEP RESISTANCE OF HIGH -PURITY CHROMIUM IN ARGON

The creep properties of a pure chromium have been investigated in argo n by comparing with those in air at 1273K in the stress range of 14.7 to 58.8MPa. The minimum creep rate of the pure chromium in argon was n early equal to that in air at higher stresses, but at lower stresses t he minimum creep rate in argon was larger than that in air and the dif ference in the minimum creep rates between in argon and in air became larger at lower stresses. Nitrogen content of the specimen interrupted at the minimum creep rate in air increased with decreasing the stress . The minimum creep rate of the specimens pre-aged in air at 1323K for 3.6 x 10(1) to 3.6 X 10(3)ks, was investigated by carrying out creep test at 1273K and 49.OMPa in argon. The minimum creep rate of the pre- aged specimens decreased with the increase in nitrogen content. The re sults conclusively demonstrate that the higher creep resistance of the specimens crept in air than that in argon at lower stresses is mainly attributed to the solid solution strengthening of nitrogen due to nit riding. to nitriding.