Improvement of mechanical properties of diffusion- and prealloyed sintered steels by heat treatments.

Fatigue tests were performed and compared to the constituents of the microstructure on specimens in notched and unnotched conditions, manufactured from diffusion-alloyed (Distaloy AE) and prealloyed powder (Astaloy A) with two different carbon contents and heat-treated by conventional quenching and tempering as well as isothermal transformation under several conditions. The aim of the investigation was to attain endurance limits of 150 MPa and more on notched samples which simulate actual parts geometries and ultimate tensile strengths in the range between 900 and 1100 MPa. This goal was achieved for several combinations of material composition and heat treatment.