Duplex Surface Treatment of Pearlitic Ductile Iron for Diesel Crankshaft 2005-01-1693

In comparison with forged steel, the Pearlitic Ductile Iron (PDI) for diesel engine crankshaft is limited by its low bending fatigue strength. Nitriding followed by fillet deep rolling introduced in this paper is proved to be an effective way to improve the fatigue properties. Two types of crankshafts of turbocharged and intercooled diesel engines were investigated with this method. The PDI material used in both cases was as-cast QT700-2 with a nominal tensile strength of 700MPa and elongation no less than 2%. Bending fatigue tests have shown that the bending fatigue limits of the duplex treated PDI crankshafts were equivalent to those of the fillet hardened steel ones. The feasibility of the application of the duplex treated PDI to the medium-and heavy-duty diesel engine crankshafts has been validated by the results of users' road tests as well as engine tests.