Intermetallic powders of Ni-Al, Cu-Al and Cr-Al systems obtained by the self-disintegration method

The intermetallic compounds of the Ni-Al, Cu-Al and Cr-Al systems are characterised by the profitable set of mechanical and physical properties, such as good abrasion resistance, high temperature oxidation and sulfur corrosion resistance. Alloy powders, among them intermetallic powders, are widely used and methods of their production are under development. The technology described here takes advantage of a natural phenomenon, i.e. self-disintegration which takes place in alloys containing Al4C3 carbide, e.g. in high aluminium cast iron. The result of chemical reaction between this carbide and moisture are products of bigger volume. It causes cracking of the matrix, i.e. self-disintegration into a powder. The physical-chemical principles of the powder production using self-disintegration are presented in this article. In Ni-Al-C, Cu-Al-C and Cr-Al-C alloys, Al4C3 phase is not present in the liquid melt. Therefore, the presence of a catalysing component, increasing the chemical activity of carbon, is required. Iron can be one of such additions. The mechanism of the influence of the iron on the Al4C3 carbide crystallisation and the physical-chemical properties of the powders obtained by the self-disintegration process is presented in this work. Applications (plasma spraying, powder metallurgy) of the intermetallic powders obtained in this way are mentioned. (C) 2001 Elsevier Science B.V. All rights reserved.