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A quantitative metallographic study was performed using transmission electron microscopy (TEM) to describe the microstructural changes in a 12% chromium steel (X 20 CrMoV 12 1) during creep at 650°C. The creep experiments were conducted under constant load conditions corresponding to initial stresses of 175 and 80 N/mm2. The heat treatment for this steel consists of austenitizing followed by tempering which results in a high density of free dislocations within small elongated subgrains with carbides on or very near some of the subgrain boundaries. During creep, the mean subgrain size increases for both the high and low stress levels. Carbide particle coarsening is observed for the low stress level. These processes result in a softening of the microstructure during creep deformation.

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Practical expressions for the mean escape depth, the information depth, and the effective attenuation length in Auger-electron spectroscopy and x-ray photoelectron spectroscopyThe current passing through a cell, silver/silver halide/graphite, has been measured as a function of applied potential in the temperature range between 200 and 370°C, for potentials less than O.S volt. Under these conditions, the current for steady-state conditions is mainly electronic. Definite results were obtained for AgBr and AgI, but not for AgCl because of sluggish approach to steady-state conditions. From an analysis of the current-potential curves it is concluded that excess electron conduction prevails in AgBr, but hole conduction in Agl.

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