Effect of nickel content on microstructure and heat resistance of high chromium cast iron
Microstructure and heat resistance of three high chromium cast irons with different nickel contents(0.65％,1.5％,and 3.05％)were studied by means of X-ray diffraction(XRD),optical microscope(OM),scanning electron microscopy(SEM),high-temperature oxidation resistance test and high-temperature thermal fatigue test.The results show that the phases of the three high chromium cast irons are all austenite,martensite and(Cr,Fe)7C3 carbides,and the increase in nickel content leads to an increase in austenite content and a decrease in martensite content.The microstructure of the high chromium cast irons is composed of pre-eutectic dendrites and eutectic structures between dendrites,and the increase in nickel content leads to coarsening of dendrites and refinement of eutectic structures.In the high-temperature oxidation resistance test,with the increase of nickel content,the oxidation mass gain of the high chromium cast irons decreases,and the thickness of the oxide layer decreases.The oxide layer of the three high chromium cast irons has two layers,inner and outer.The main elements in the outer layer of the high chromium cast irons containing 0.65％and 1.5％nickel are O and Fe,while the main elements in the inner layer are O and Cr.The main elements in the outer layer of the high chromium cast iron containing 3.05％nickel are O and Cr,while the main elements in the inner layer are O and Fe.In the high-temperature thermal fatigue test,the main cracks of the three high chromium cast irons all extend along the V-shaped notch,and the length of the main cracks decreases with the increase of nickel content.The thermal fatigue resistance of the high chromium cast iron containing 3.05％nickel is 36％higher than that of the high chromium cast iron containing 0.65％nickel.
NETL
NSTL
万方数据
