THERMOPHYSICAL PROPERTIES OF SINTERED STEELS: EFFECT OF POROSITY

Reliable data for the thermophysical properties of sintered steels, in particular the coefficient of thermal expansion (CTE) and thermal conductivity (TO), are critical in the design of components and for modeling heat-treating processes. There are contradicting opinions about the effect of porosity on these properties. In the present work, it is shown that, for a powder metallurgy (PM) molybdenum prealloyed steel, CTE, measured by dilatometry up to 1,000 degrees C, is virtually independent of porosity over a density range from 5.97 g/cm(3) to 7.53 g/cm(3). Also, there is no effect of the sintering regime. TC was determined over the same temperature range based on measured thermal diffusivity, specific heat, and density. TO was found to depend on porosity, but the effect over the technically relevant density range was less pronounced than the effect exerted by alloying elements in standard steel grades in the low-to-medium temperature range. Thus, both thermophysical properties of sintered steels are less influenced by porosity than by composition, and behave more like wrought steels than is generally assumed.