Effect of bainite on mechanical properties of nickel-chromium constructional alloy steels

In this paper the influence of different percentage of bainite on the mechanical properties of nickel-chromium steel has been investigated. Hardness was found to decrease with the increase of bainite in the microstructure at all temperatures of investigation and after complete transformation in the range of 500°C-350°C minimum hardness was observed at 450°C for all percentages of bainite. The cause of minimum hardness at 450°C was investigated. Similar observations were also made in the tensile strength curves. Moreover, a comparative study has been made between mechanical properties of 100% bainite and quenched and tempered products. The mechanical properties of 100% bainite was always inferior to that of quenched and tempered products, excepting those formed below about 400°C. (Messrs R.K. Dubey, Scientist, S.P. Chakraborty, Senior Laboratory Assistant and P.K. Gupte, Scientist, National Metallurgical Laboratory, Jamshedpur)