Influence of compositions and heat treatment on metastability of structure and properties of wear-resistant cast irons of the Fe-Cr-Mn-C system

Abstract

The influence of chromium, manganese, carbon content and quenching modes on the formation of the structure, metastability of austenite and properties wear-resistant cast iron alloying system Fe-Cr-Mn-C with small additions of titanium, copper, silicon in various variations was investigated. The metallographic, durometric research methods, tests for dynamic bending, impact-abrasive wear resistance were applied. The regularities of changes in the phase composition and microstructure under the influence of the heating temperature for quenching in the range from 920 to 1070 °C with cooling in sand have been established. With an increase in the heating temperature for quenching in the structure of cast irons, the content of austenite increases and the content of quenching martensite decreases. The amount of carbide phases of compositions (Fe, Cr)3C, (Cr, Fe)7C3, (Cr, Fe)23C6 and titanium carbonitrides TiCN, depending on the content of carbon and alloying elements, as well as the heating temperature for quenching, varies within 20...35 %. A significant contribution of deformation induced phase transformations - martensitic, dynamic aging, occurring in the surface layers in the process of testing in the formation of impact-abrasive wear resistance of cast irons was revealed. It is characterized by the effects of deformation self-hardening, manifested in the increase in the hardness of the surface (working) layer within HRC = 2...9 and relaxation of microstresses. The formation of optimal martensitic-austenitic-carbide metastable structure could be provided at the optimal ratio of alloying elements and under the influence of heat treatment at which the effect of deformation self-hardening at wear that increases drastically the wear resistance of the investigated cast irons could be realized. The developed cast irons of optimal compositions have shown high economic efficiency in the production of working bodies of shot-blast machines, sand-throwers, protective lining plates of sintering-blast furnace equipment. They can be recommended for the manufacture of various high-wear machine parts of machines operating under conditions of impact-abrasive andabrasive wear.