Method for imaging inclusions in investment castings

Abstract

A metal or metal alloy article is cast using an investment casting mold where the mold facecoat, and perhaps one or more of the mold backup layers, comprises an imaging agent distributed substantially uniformly throughout in amounts sufficient for imaging inclusions. The facecoat preferably comprises an intimate mixture of a refractory material and the imaging agent. Intimate mixtures can be produced in a number of ways, but a currently preferred method is to cocalcine the refractory material, such as yttria, with the imaging agent, such as gadolinia. The facecoat also can comprise plural mold-forming materials and/or plural imaging agents. The difference between the linear attenuation coefficient of the article and the linear attenuation coefficient of the imaging agent should be sufficient to allow imaging of the inclusion throughout the article. The metal or metal alloy article is then analyzed for inclusions by N-ray analysis. The method also can include the step of analyzing the metal or metal alloy by X-ray analysis. The imaging agent, typically a metal oxide or salt, comprises a material selected from the group consisting of boron, neodymium, samarium, europium, gadolinium, dysprosium, holmium, erbium, ytterbium, lutetium, iridium, physical mixtures thereof and chemical mixtures thereof.