A PROCEDURE FOR DETERMINING THE CHANGE OF MATERIAL FATIGUE RESISTANCECHARACTERISTICS IN LONG-TERM OPERATION

The present model is based on experimentally determined dependence of fatigue resistance, for specimens mens and gas turbine blades (in long -term operation) on a depth of unalloyed surface layer. An algorithm h as been developed for forecasting processes of material dealloying, to fit the arbitrary time-temperature operation regime. The model predic ts the distribution of alloying elements in the metal surface layer an d oxide film through the solution of direct and inverse problems of di ffusion. Diffusion parameters are determined by experimental data, mea sured using electron probe microanalysis (EPMA), of element distributi on after exposure in the specified corrosion-aggressive environment at several temperatures during a relatively short time. Knowing the law relating fatigue resistance to dealloying depth, material fatigue resi stance is predicted after arbitrary specified time and temperatures of operation. Good agreement between calculation, by this model, is obse rved from the results of an operation during 60000h.