Obtaining of High Cr Content Cast Iron Materials

Abstract

View the article online for updates and enhancements. Abstract. We have obtained, through the classic casting process, 3 highly chromium-based experimental alloys proposed for replacing the FC 250 classical cast iron in braking applications. Casting was carried out in an induction furnace and cast into moulds made of KALHARTZ 8500 resin casting mixture and HARTER hardener at SC RanCon SRL Iasi. It is known that the microstructure of the cast iron is a combination of martensite with a small amount of residual austenite after the heat treatment of the ingot. In the case of high-alloy chromium alloys, the performance of the material is due to the presence of M7C3 carbides distributed in the iron matrix Resistance to machining and deformation is based on alloy composition and microstructure, while abrasion resistance will depend on properties and wear conditions. IntroductionFriction between two dry surfaces in contact and moving relative to each other is known as Coulomb friction and even if it is a phenomenon that occurs several times a day the frictional force can only be estimated from previous experience and experimental results [1].In the case of braking systems (for any type of vehicle using braking systems) the contact surfaces are often covered with different materials to result in a sliding process and are not just two metallic materials sliding over each other. The metallic surface will be affected by abrasion, adhesion of compounds other than the base material, or deformation of the material during sliding, which will create metallic fragments of material as well as other particles [2].Any metal friction surface, even if it appears geometrically fine at a macroscopic level, is quite rugged on a microscopic scale, with a large distribution of roughness along it. An explanation of friction formation is the interaction of microscopic asperities of two surfaces, but when two such surfaces are forced to slide one on the other, it is very difficult to specify where and how contact occurs between them.Even if, from the point of view of an engineer, it can be assumed that a coefficient of friction between two surfaces, especially metallic, sliding one at the other, can be considered constant in the applicative work with the braking systems, it is very important to understand that this coefficient The friction is variable and it is very useful to understand why [4,5]. There are several reasons why the braking performance of a vehicle can change over time and any damage can be recognized by the user through a reduction in braking parameters such as distance or vehicle stopping time [6][7][8].Alloy cast iron with a high percentage of chromium are recognized as having a high wear resistance and have been widely used for wear-affected parts operating under extreme conditions. Exceptional wear resistance of Cr-rich castings results primarily from the high percentage of M7C3 carbides formed in the ferrous matrix with M = Fe, Cr and which have the role of preventing graphite formation and generally stabilize carbides [1...

Investigation on the Influence of Tempering on Microstructure and Wear Properties of High Alloy Chromium Cast Iron

“…The multiple impacts may damage the ball and reduce the efficiency of the grinding. The mechanical stresses are incurred of diverse origins: shearing due to contact with the wall of the mill, contact between the balls, peeling caused by wear and shock [5][6][7][8][9][10].…”