Characterization of Casting Defects in Typical Castings of a Directionally Solidified Superalloy

摘要

A program was conducted to assess the effects of casting defects in directionally solidified (DS) material. The technical approach involved two tasks, the first including the characterization of typical casting defects in F-100 1st and 2nd stage PWA-1422 production turbine blades and the second including the evaluation of thin sheet test specimens cast deliberately to contain defects. The defects included microshrinkage, inclusions and grain misorientation and represented a range of severity levels including conditions exceeding current production acceptance criteria. The analysis of production castings indicated that substantial decreases in the rejection rate could be achieved with only minor relaxation of the acceptability criteria. In addition, dross inclusions were found to be the single most frequent cause for casting rejections.