Effect Of Pour-over Technology And Feeding Cored-wire Technology On Microstructure And Mechanical Properties Of Carbidic Austempered Ductile Iron With Chromium

Carbidic Austempered Ductile Iron(CADI) is new materials that based onAustempered Ductile Iron(ADI) by adding a small amount of carbide formingelements (such as Cr, Ti, V, Mo, W, etc.) in melting process, which not only reserveshigh strength and impact toughness of ADI and also has the advantage of higher wearresistance, especially suitable for application in mine mechanical grinding balls, plateand so on.Produce CADI as-cast with Cr by using Pour-over technology and FeedingCored-Wire Technology. This article compared organization and performance of as-cast sample and isothermal quenching heat treatment sample with different Cr joinamount in two methods by using metallographic microstructure observation,scanning electron microscope and X-ray diffraction analysis, hardness, impacttoughness, tensile strength and wear resistance test method.The results shows that the as-cast sample graphite form produced by FeedingCored-Wire Technology is smaller and rounder than by Pour-over technology withsame amount of Cr. When Cr increases to more than0.8%, sample carbide producedby Feeding Cored-Wire Technology is less than by Pour-over technology. With theincrease of the amount of Cr, as-cast sample performance of the hardness increases,the impact toughness decreases and tensile strength reduced. Increment rate ofhardness by Feeding Cored-Wire Technology is lessen and impact toughness andtensile strength are largen than by Pour-over technology.Performance of CADI are both hardness increase, toughness and tensile strength decrease, fracture types change from ductile fracture to brittle fracture with theincrease of Cr after heat treatment of920℃austenitizing insulation1.5hour and280℃isothermal quenching2hour by two methods. With the increase of the contentof Cr, increment rate of hardness by Feeding Cored-Wire Technology is also lessenand impact toughness and tensile strength are also largen than by Pour-overtechnology. Increase percentage of toughness and tensile strength increased from17.1%to73.2%and from1.04%to8.50%.Abrasion resistance of CADI heighten and wear types transform from a seriousabrasive wear into the adhesive wear with the increase of Cr. Wear resistance of theCADI differs not obviously when the amount of Cr is under0.6%by two technology.Above that, wear resistance by Pour-over technology is higher. Compared withseveral traditional mine wear-resisting material, CADI has better comprehensiveadvantages of higher tensile strength and hardness, better impact toughness and wearresistance. Introduce of Feeding Cored-Wire Technology expands application field ofCADI.