Study On Wear Resistance Of Austenitic-Bainitic Ductile Iron

In this paper, under the conditions of austenitized at tempera-tures ranging from 850℃to 950℃and austempered at temperatures ranging from 260℃to 420℃, the austempering treatment of ductile iron was conducted. A series of specimens made of austenitic-bainitic structure having different relative volume fraction, different shape and distribution of these two constituents were obtained. The wear behavior of ADI with different hardness was investigated under the conditions of sliding and rolling wear with lubricating and impact abrasion. And the wear mechanism of ADI was studied. The results showed that with increasing austenitizing temperatures(850~950 ℃) and austempering temperatures(300~400℃) the wear resistance of ADI in lubricated sliding friction decreased,and the wear mechanism was mainly adhesive wear;With increasing austempering temperatures the wear resistance of ADI in lubricated rolling friction decreased to a value, and then increased. And the wear mechanism was a process of pit-shaped fatigue spalling. In the present paper it is proposed that the wear resistance of ADI is a synthetical result of the shape, distribution, amount and stability of retained austenite, as well as the shape and distribution of bainite, and the hardness and toughness of ADI itself. It's emphasized that a certain amount of retained austenite which envelopes bainite rods with a shape of thin film and fine pieces is favourable to the improuement of the wear resistance of ADI. But too much austenite with continuously blocks jioned is harmful to the wear resistance of ADI. In the meantime, fine bainite is favourable to the wear resistance of ADI while coarse bainite is disadvantageous. It's effective to improve the shape and the distribution of austenite and bainite by lowering austenitizing temperatures and austempering temperatures properly. On the other hand, the influence of graphite on the wear resistance of ADI was discussed. Fanally, some suggestions were made for selection of ADI to suit various wear conditions.