Failure analysis of gray iron pump housings

Abstract

Hydrostatic pressure testing of several large gray iron castings resulted in brittle overload failures. Subsequent failure analysis on two of the failed components revealed casting imperfections associated with the failure origins. In each case, the root cause of failure was related to the casting mold. The first incident involved an imperfection that resulted in a stress concentration that reduced the normally large critical flaw size to the microstructural level. A microstructural gradient adjacent to the fracture of the second casting was the result of an inadequate mold design that allowed for rapid cooling at a thin-walled region of the casting. Material selection was a concern of the manufacturer and was also investigated.