Once the mold has cooled, any accessible sprue and gating is cut away. Then, through a combination of hammering, blasting, and etching, the remaining shell and ceramic core come off the finished part. Boutot said that any hammering is kept light to avoid part damage. But high-pressure water jet blasting and chemical etching gnaw away at any tenacious bits of shell and ceramic core to reveal a smooth casting. Finally, it's on to a series of nondestructive tests, such as ultrasonic wall thickness checks and fluorescent dye penetrant exams.
Dimensional inspection follows.
Then, a combination of heat treating, hot isostatic pressing, machining, or coating completes the journey. The Growth of Crystals In an equiax turbine blade, the grain boundaries control the strength, said John Corrigan, Howmet's vice president of engineering. Creep is the principal failure mode. For equiax crystals, failure occurs ultimately at the grain boundaries. Grain structures are visible.