Effect of austempering conditions on the microstructure and tensile properties of low alloyed sintered steel

Because of the combination of strength and toughness, much interest has been focused on austempered sintered low-alloyed steels. Implementation of this treatment for powder metal components has been limited by interaction between the open porosity of the material and the cooling fluid. This work discusses the influence of different austempering environments and parameters on the microstructure and, as a consequence, on the final properties. The sintered steels selected are based on two different prealloyed powders, Fe-1.5Cr-0.2Mo and Fe-1.5Mo, with the addition of 0.6 wt pct graphite. Green samples with medium density (7.3 g/cm(3)) were sintered at 1393 and 1523 K (1120 and 1250 A degrees C) to ensure a decrease in open porosity. The austempering treatment process requires austenitizing at 1133 K (860 A degrees C) for 2 hours followed by quenching in different baths at 563 K (290 A degrees C). The final strength and ductility are dependent upon the relative amounts of ferrite, pearlite, and bainite phases present in the austempered steel. Discussion of the experimental results compares the as-sintered and the austempered observations as well as the relationship between mechanical properties and the phases present in the final microstructures.

powder-metallurgy steel; mechanical-properties; warm compaction; youngs modulus; heat-treatment; fluidized-bed; high-carbon; p/m steels; deformation; temperature

Effect of austempering conditions on the microstructure and tensile properties of low alloyed sintered steel Articles