EFFECT OF CHEMICAL COMPOSITION AND HEAT TREATMENTS ON THE MICROSTRUCTURE AND WEAR BEHAVIOR OF MANGANESE STEEL Souad Ayadi and Ali Hadji Foundry Laboratory, BADJI Mokhtar University - Annaba, BP 12, 23000 Annaba, Algeria Copyright Ó 2020 American Foundry Society https://doi.org/10.1007/s40962-020-00479-2 Abstract The present paper analyzes the effect of the chemical composition and heat treatments on the microstructure and wear resistance of manganese steels. The studied steels are melted in an electric arc furnace. Alloying elements (Cr ? Ni ? Nb) are added as ultra-fine powder in a well- heated ladle. Samples are subjected to two heat treatments: one at 1100 °C and the other at 1050 °C, and then quen- ched in water. Optical microscopy, scanning electron microscopy and X-ray diffraction are used to evaluate the microstructural changes. Hardness and microhardness measurements, mass loss and friction coefficient were also performed to determine the wear behavior of the studied steels. The results indicated that the microstructure of the manganese steel in the as-cast state consists of an auste- nitic matrix and cementite alloyed with manganese and chromium ((Fe,Mn,Cr) 3 C). Increasing chromium content increases the size of the alloyed cementite (Fe,Mn,Cr) 3 C. Addition of niobium leads to the apparition of new sec- ondary carbide (NbC). The heat-treated microstructures consist of martensite, retained austenite and a small quantity of precipitates. Increasing in heat treatment tem- perature and addition of alloying elements (Cr ? Ni ? Nb) increase the hardenability of the studied steel and favor the martensitic transformation. As a result, addition of niobium and increasing in chromium and nickel contents improve hardness and wear resistance of the studied manganese steel. Keywords: manganese steel, chemical composition, heat treatments, microstructures, wear resistance Introduction Manganese steel, containing 1.2% C and 12% Mn, is the most widespread use in wear field applications. It was discovered in 1882 by the metallurgist Robert Abbot Hadfield. 1–3 The latter then took the name of its inventor: Hadfield steel. Compared with most other wear-resistant ferrous alloys, manganese steel has a superior toughness and a moderate cost. This steel is known for its interesting mechanical properties. It combines hardness and ductil- ity. 4,5 This steel does not have a high enough hardness, but it is characterized by its remarkable work-hardening capacity under impact. It is also known for its excellent wear resistance especially for applications involving metal–metal contact. Dry contact at low temperatures between a metal and Hadfield steel gives a harder contact surface. 6–8 Compression loads, rather than shocks, provide deformation of the contact surface. As a result, manganese steel not only wears less than other steels when it is in contact with other metals, but it also develops a hard surface and offers a good resistance to friction. 9,10 These features generally make it widely used for various wear- dominated industries, namely cement plants with mining, crushing, grinding and sizing operations, quarries and the recycling industry. 11,12 In the as-cast state, manganese steel has an austenitic matrix with complex carbides precipitated at the grain boundaries. 13,14 In this state, its hardness is generally low, associated with an average wear resistance. 15,16 Hardening under the effect of chemical elements is one of the best known methods for this type of steel. The addition carbide forming elements to manganese steel improves its hardness and wear behavior. 17–20 In this paper, microstructural changes and wear behavior of manganese steel alloyed with chromium, nickel and nio- bium before and after heat treatments have been studied and compared to manganese steel. International Journal of Metalcasting