Effect of Holding Time on Strength and Abrasion Resistance of Cu-Ni-Mn Alloyed Permanent Molded Toughened Austempered Ductile Iron For Automotive Gear Applications.

摘要

Dry sand abrasion and erosion tests on permanent molded austempered ductile iron (ADI) samples subjected to special austempering heat treatment (QB~1 process) are being studied and reported. The oil quenched permanent moulded ductile iron samples were re-heated and held at (α+γ) temperature range prior to austempering in a salt bath resulting in permanent moulded toughened austempered ductile iron (PMTADI). The PMTADI samples were alloyed with 1% each of copper, nickel and manganese content. The holding time in the (α+γ) temperature range were varied at 60, 90, 120 and 150 minutes. Results indicated that the abrasion resistance was highest for 1% Cu-Ni-Mn alloyed PMTADI samples subjected to 120 minutes holding time in the (α+γ) temperature range. The retained austenite content and the distribution of bainite in the matrix played a major role on the abrasion resistance of PMTADI. There was about 12% increase in the abrasion resistance for 1% Cu-Ni-Mn PMTADI samples as compared to unalloyed PMTADI samples and about 22% increase in abrasion resistance than as cast ductile iron samples. The optimum holding time in the (α+γ ) temperature range for enhanced abrasion resistance was found to be 120 minutes. The results were analyzed based on structure property correlations and the distribution of bainite.