Methodology of quantitative evaluation of porosity, dendrite arm spacing and grain size in directionally solidified blades made of CMSX-6 nickel alloy

Modern nickel-based alloys are constructional materials used in the production of parts of aircraft engines. The paper presents the results of studies of nickel superalloy CMSX-6 used for the manufacture of blades for turbojet engines. The scope of the study encompasses a development of a quantitative evaluation methodology regarding the blade's porosity and primary structure, as well as an analysis of the influence of the location of material sampled for the study on the results of a quantitative evaluation of the structure. Parallel columnar crystals, characteristic for a correct solidification process during directional crystallization, were detected on the surface of the product. It has been found that porosity of the investigated blades does not exceed 0.145%, which is a sufficient value to fulfil the acceptance requirements for casts. The transitory region between the blade root and airfoil is an area of the highest porosity. In addition, an influence of the size of the blade's plane cross-section on the spacing of dendrite secondary arms in the cast has been evidenced.