WEAR BEHAVIOUR OF PLAIN CARBON DUAL PHASE STEEL

Abstract

The need to minimize both material and energy losses in mechanical systems has led to an enlarged interest in the field of "Tribology", the science of friction, lubrication and wear. The aim of the present investigation is to analyze the wear behaviour of dual phase steels in the context of its charactristic microstructure as observed in the configuration of a Timken machine. Examples are presented here of ferrite-martensite mixtures designed for optimum combinations of high strength, toughness and wear properties in plain carbon steels, e.g. for mining, mineral processing, agricultural and pipe line applications. In view of the above, dual phase steels are developed by intercritical annealing treatment of normalized plain carbon steel at 740°C for holding times I hr, 10 min, 5 min and designated in the present investigation as 'Steel I', 'Steel II' and Steel III respectively. Normalized steel designated as steel IV is also developed. Normalizing heat treatment is carried out at 910°C for 5 min followed by air cooling. Wear characteristics of the dual phase and normalized steel are determined by Timken machine at different loads viz. 4, 6, 8 kgf and sliding velocities ranging from 25.67x10-2 to 51.39x10-2m/sec. With increase in load the wear volume is observed to increase continuously but with an increase in sliding velocity it is observed to decrease in the range of velocities under investigation. To understand the wear mechanism, wear tracks have been studied under SEM and roughness of the wear tracks has been measured to supplement the wear results. Comparative studies of dual phase steels have also been done with normalized steel. It is observed that dual phase steel has superior wear resistance than that of normalized steel. It due to ferrite-martensite structure which exhibits high work-hardening rate and good toughness compared to ferrite-pearlite structure. It is also observed that among different dual phase steels (Steel I, II, and III) developed, `steel II' has the best wear