Towards more reliable investment castings

Abstract

The need for more reliable investment castings to meet the expectations of end users is outlined and the research undertaken during the Fundamentals of Investment Casting (FOCAST) project to meet this requirement is summarised. The traditional gravity poured, top gated mould designs used widely by the investment casting industry are shown to produce the least reliable aluminium alloy and steel castings. Changing to a bottom gated design to minimise surface turbulence during mould filling leads to a significant improvement in reliability, although the mould designs may not be particularly easy to implement in practice. It has been shown that a correctly used tilt pouring technique can also reduce surface turbulence and thereby improve reliability, and it is considered that this process is worthy of further development and evaluation by the investment casting industry. Countergravity mould filling has also been shown to be capable of producing more reliable castings than conventional gravity casting. The three techniques are compared and their industrial implementation discussed.