Study On Microstructures And Properties Of RE Modified High Chromium Cast Iron

A modifier is designed and employed to the high Cr cast iron. The effects of modification on microstructure and mechanical properties have been investigated, and the mechanism of the modification was proposed and discussed from different aspects. Influence of Ni on microstructure and mechanical properties of modified high Cr cast iron was studied. Sliding wear and abrasive wear is studied under different circumstances to evaluate the wear resistance of high chromium cast iron.The results are as follows:(1) Modification treatment refines the primary austenite of high-chromium cast iron and makes the austenite turn into equiaxed grains, after modification, martensite content increased; M7C3type eutectic carbide grain size decreases, and the continuous net-like structure of carbides are broken partially, and become isolation, blocky and stripy. Hardness of high Cr cast iron increase6HRC for modified alloy compared with the non-modified alloy, no significant change in impact toughness. After heat treatment, hardness and impact toughness of the modified alloy increase, impact toughness of the modified high-chromium cast iron can be achieved9.7J/cm2after950℃/2h heat-treatment,5J/cm2higher than the non-modified high chromium cast iron.(2) The sliding wear test for the modified and non-modified high Cr cast iron show that at low load, the wear loss for the both irons are smaller, with no obvious difference between the modified and the non-modified iron; at higher load, the modified iron show better wear resistance than the non-modified iron..(3) For the modified high Cr cast iron, increasing nickel is conducive to get more residual austenite and relative smaller carbide, but the primary austenite size become larger; the matrix of the high Cr cast iron is mainly austenite, with no martensite. Increasing of nickel content makes in impact toughness but decrease in hardness of the modified high chromium cast iron. After heat treatment of900℃, the toughness can be achieved11.7J/cm2. (4) The abrasive wear test indicate that the heat treatment can make the wear resistance of high chromium cast iron significantly improved. Wear is independent with the hardness, but mainly depends on the number of precipitated secondary carbide during heat treatment and the matrix micro-hardness. The experimental results show that the steel casting high chromium cast iron after900℃/2h treatment has the minimum wear loss, showing the best wear resistance.