Microstructures, Compressive Residual Stress, Friction Behavior, and Wear Mechanism of Intensive Quenched Ductile Iron

The intensive quenching process effectively reduces the quenching cracking tendency of ductile iron and significantly enhances its hardness. In this paper, the tribological behavior of ductile iron intensively quenched (DI_IQ) and intensively quenched and tempered (DI_IQAT) (tempering temperature 180 °C) at different austenitizing temperatures (880 °C/910 °C/940 °C) is investigated, alongside carbon steel for comparison. The microstructure of ductile iron intensively quenched specimens consists of martensite and graphite, with the optimal quenching process identified as intensive quenching at an austenitizing temperature of 910 °C. DI_IQ (910 °C) shows a finer and more homogeneous microstructure, higher hardness, a compression-stressed surface, and improved wear resistance. In the ductile iron intensively quenched low-temperature tempered specimens, the microstructure consists of tempered martensite and graphite. DI_IQAT (910 °C + 180 °C) also exhibits a finer microstructure, higher hardness, better impact toughness, and better wear resistance. In addition, the friction coefficient curves for DI_IQ and DI_IQAT consistently remain lower than those of oil-quenching and tempering carbon steel, and the relative wear rate of DI_IQAT is 25% of that of carbon steel. The surface morphology indicates that the main wear mechanisms for DI_IQ and DI_IQAT are abrasive and oxidation wear.