A Pooled Analysis of Heat-Resistant Cr-Al Steels

Background. Under the conditions of rapid heating-cooling, nonuniform temperature fields occur in the volume of the part that contribute to the accumulation of thermal stresses. Such stresses may exceed the yield point of the alloy and destroy part's material. The form of parts' destruction depends on the properties of metal and operating conditions. A typical form of destruction is cracking. It was determined by the analysis of operation of thermal-resistant parts that the choice of alloy with high oxidation resistance is necessary, but not enough to provide the specified life of thermal-resistant items, since in thermal cycling conditions heat resistance of metal begins to appear primarily. Objective. The aim of the work is to establish the effect of carbon and rare earth metals on heat resistance of thermal-resistant Cr-Al steels for work in extreme conditions and the study of the kinetics and mechanism of destruction of metal. Methods. Samples of90 mm in length and12 mm in diameter were subjected to heat treatment in a box furnace to 1100 °C, and chilled under running water. Assessment of heat resistance was done with the appearance of thermal fatigue cracks on the side surface or at their ends. Phase composition and structure were investigated by modern X-ray diffraction and metallographic methods. Results. The mechanism and kinetics of the destruction of cast metal under conditions of thermal cycles were determined. The selection of Cr-Al steel for work under extreme conditions should be made with regard to its mechanical, physical, physico-chemical and technological properties, as well as the design features of a particular casting. Conclusions. To achieve high heat resistance in the conditions of high variable temperatures Cr-Al steel should comprise 25?30 % of Cr, 1.0?3.0 % of aluminum, 0.3?0.6 % of titanium, 0.2?0.4 % of C and 0 15?0.40 % of rare earth metals.