Abstract
In this paper, the effect of deep cryogenic treatment in combination with conven- tional heat treatment process was investigated on microstructure and mechanical behaviors of alloyed bainitic ductile iron. Three processing schedules were employed to treat this alloyed ductile iron including direct tempering treatment, tempering.+deep cryogenic treatment and deep cryogenic treatment.+tempering treatments. The microstructure and mechanical behavior, especially the wear resistance, have been evaluated after treated by these three schedules. The results show that martensite microstructure can be obviously refined and the precipitation of dispersed carbides is promoted by deep cryogenic treatment at .−196 ∘ C for 3 h after tempered at 450 ∘ C for 2 h. In this case, the alloyed bainitic ductile iron possesses rather high hardness and wear-resistance than those processed by other two schedules. The main wear mechanism of the austempered alloyed ductile iron with deep cryogenic treatment and tempering is micro-cutting wear in association with plastic deformation wear.
Highlights
Bainitic ductile irons have long been considered candidate materials for wear-resistant components in mining and minerals industry due to their excellent impact toughness, strength and abrasion resistance provided by the bainite, eutectic carbides and graphite in the microstructure [1, 2]
By using optical microscopy (OM), scanning electron microscopy (SEM) and X-ray diffraction (XRD), the effect of different cryogenic treatment sequence together with tempering treatment on the matrix structure, hardening behavior and wear resistance of austempered alloyed bainitic ductile iron was investigated in this paper
The optical microstructure of the alloyed bainitic ductile iron under the austempered condition is shown in Fig. 1 Typically, the austempered alloyed bainitic ductile consists of discontinuous eutectic carbide, acicular bainite, residual austenite, martensite with graphite dispersed in the matrix [11]
Summary
Bainitic ductile irons have long been considered candidate materials for wear-resistant components in mining and minerals industry due to their excellent impact toughness, strength and abrasion resistance provided by the bainite, eutectic carbides and graphite in the microstructure [1, 2]. Higher strength and hardness can be obtained by adding Cr and V as alloying elements In order to further improve the hardness and wear resistance of the cast iron, the deep cryogenic treatment, as an effective way, can be used to modify the microstructure. As far as deep cryogenic treatment in combination with conventional heat treatment is concerned, till there has been little information available for alloyed bainitic ductile iron. By using optical microscopy (OM), scanning electron microscopy (SEM) and X-ray diffraction (XRD), the effect of different cryogenic treatment sequence together with tempering treatment on the matrix structure, hardening behavior and wear resistance of austempered alloyed bainitic ductile iron was investigated in this paper. The results are presented and a discussion was made with an attempt to correlate the mechanical behavior with microstructures
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