Comparison of impact-abrasive wear characteristics and performance of direct quenched (DQ) and direct quenched and partitioned (DQ&P) steels

The recently developed method of direct quenching and partitioning (DQ&P) was utilized to produce ultra-high strength martensitic steels with retained austenite. The DQ&P steels have high surface hardness while retaining good impact toughness and elongation values. The toughness and elongation properties are attributed to the retained austenite which is stabilized in the DQ&P process. The aim was to study if DQ&P processing could be utilized for improved abrasive wear resistance. Two medium-carbon (0.3%) chemical compositions were selected with varying amounts of silicon, aluminum and chromium. The processing route for DQ&P involved interrupted water quenching with two different quench stop temperatures (T-Q) (175 and 225 degrees C). Direct quenched (DQ) variants were also produced for comparison of both mechanical properties and wear characteristics. Compared to the DQ treatment, improved impact toughness and elongation to fracture were achieved with the DQ&P treatment while initial strength and hardness was reduced. An impeller-tumbler testing device was used to measure the impact-abrasive wear performance of the different experimental microstructures and compared with that of a reference commercial 500 HB steel. No advantage of the increased ductility of the DQ&P steels was apparent; wear resistance was shown to only correlate with the initial surface hardness of the steels.