Experimental Analysis of Mechanical Properties, Wear and Corrosion Characteristics of IS500/7 Grade Ductile Iron Casting

Abstract

In the present research investigation, ductile iron castings conforming to IS500/7 grade casting were produced using green sand moulds. The castings were produced in a regular production foundry using 1.25T Induction Furnace. The molten metal was subjected to standard desulphurisation and modularisation to get graphite in the nodular form. Based on the earlier investigation by the above group the castings were austenitised at 900oC for 120minutes and quenched in a salt bath consisting of potassium nitrate and sodium nitratein the ratio of 55:45 and maintained at 310oC for 120 minutes to bring about austempering treatment. The result in austempered ductile iron will consist of graphite nodules in a matrix of bainite[1,2]. The effect of austempering heat treatment on microstructure, mechanical properties[13,14] andwear characteristics were studied and compared with the as-cast condition. Mechanical properties such as ultimate tensile strength, % elongation, hardness and impact strength were determined. Wear tests were carried out to determine the weight loss of specimens; using pin on disc type machine. Wear test was held for different loads viz. 300 gm, 400 gm and 500 gm and different speeds conditions viz. 950 r.p.m, 1430 r.p.m and 2130 r.p.m. Corrosion tests were carried out to determine corrosion rate at different viz. 35°C & 45°C temperature for increasing duration viz. 2 hours to 24 hours. The results of the research investigation indicate that the heat treated castings shows higher Ultimate Tensile Setength values (54.86% increase), elongation values (64.32% increase) and Brinell hardness values (19.03% increases) as compared to the ascast condition of casting. From the dry sliding wear studies, it is seen that heat treated specimen’s shows higher resistance to wear compared to the ascast specimens and corrosion rate & weight loss due to corrosion in heat treated condition is less compared to ascast ones.