Thermoanalytical techniques for characterizing sintering processes in ferrous powder metallurgy

Abstract

For powder metallurgy processing, the sintering stage, i.e. the heat treatment of a the powder compact below the melting point of -at least- the major component, is decisive for establishing microstructure and properties. Thorough studying of the chemical and metallurgical processes occurring during sintering is essential for attaining optimal product properties, and sintering has therefore been the focus of investigations for many decades. Thermoanalytical techniques, at best combined with chemical analysis, enable in-situ characterization of the sintering process from many perspectives. When using these techniques in powder metallurgy, it should be considered that the very large specifc surface of a powder compact, compared to a solid metallic body, results in much higher reactivity with the surrounding atmosphere. This atmosphere is on the one hand the “external” one, outside the body in the free space of the furnace, and on the other hand the “internal” one within the pore network of the specimen. This paper shows diferent examples of how critical information about the sintering process can be described by using thermoanalytical techniques combined with mass spectroscopy: e.g. phase transformations and liquid phase formation in the powdered compact, deoxidation and decarburization reactions, and interstitial redistribution in sintered alloy steels prepared through diferent alloying techniques.