The SEM Metallography Analysis of Vacuum Cast ZhS6K Superalloy Turbine Blade after Various Working Hours

Abstract

A vacuum cast Ni-base superalloy ZhS6K is used for the production of turbine blades whose are working in the hot section of turbine in former USSR DV-2 jet engine. The usual working temperature for this kind of alloy is designed for 800/1050°C. Turbine blades with protective alitized layer made from this alloy were evaluated at the starting stage, then after 600, 1000, 1500 and 2000 hours of regular working. The SEM methods of quantitative metallography were used for structural characteristics evaluation. The microstructural analysis shows increasing of the medium distance of secondary dendrite arms D, what is related to chemical changes in dendritic structure, and the intermetallic strengthening gamma prime phase coarse and turn into spherical shape what leads to decreasing of dislocation and precipitation strengthening mechanism and further decreasing of hot temperature properties of the alloy. The method used at quantitative evaluation and techniques of colour optical microscopy and SEM is useful when microstructure degradation of superalloys has occurred.