New Method of Controlling the Carbon Content of High Chromium Alloyed Powders during High Temperature Sintering
Atmosphere control in a continuous sintering furnace is one of the most important variables in a successful sintering process. This statement becomes even more weight when sintering of high chromium containing powders at elevated temperatures is applied. Depending on the sintering atmosphere, de-carburization at the surface of a product is almost impossible to avoid. The production of more highly loaded PM parts by sintering requires higher sintering temperatures, which in turn increases the need for controlling the carbon level, and limiting surface decarburization. One way to control the carbon level is to add CO to the sintering atmosphere and increase the carbon activity of the atmosphere. This idea has been used in conventional carburizing for decades. But is it applicable for sintering processes at temperatures up to 1250°C? The presented paper shows results of tests on Astaloy CrM bodies with additions of up to 0.6% carbon that were sintered at 1250°C in carbon monoxide containing atmospheres with and without hydrogen additions. Finally, an outlook of how this technology could be implemented in industrial scale sintering furnaces will be given.
Lucio Salgado and Francisco Ambrozio Filho
S. Ahonen et al., "New Method of Controlling the Carbon Content of High Chromium Alloyed Powders during High Temperature Sintering", Materials Science Forum, Vols. 591-593, pp. 300-307, 2008