STUDIES IN 9 Cr WHITE IRON ALLOYED WITH MANGANESE AND COPPER

Abstract

Effect of heat-treatment On the hardness, microstructure and reeietece to corrosion in a 5 +/. Nate, solution has been studied for e, 9CI white Iron alloyed with 6'/R -and 1 '/, Cu for assessing the eteotrochemical behaviour of martezeite + carbide and related microetruoturee namely martenaite + auetenito carbide # austenite + dispersed carbide + massive end austenite + massive carbide' Heat treatments, involved - air cooling and oil quenching from 900, 950,, 1000, 1050°C after 'holding at each of these temperature4 for 4, 6,8 and 10 bra respectively. Corrosiox studies were ocnfi.ned. to ail quenphed specimens Which were inves. tigated with or without a stress relieving heat treatment coneial Ing of 600°C 0.5 h followed by either air 'cooling- Or oil, quenobir It emerges that mioroetructuree based on auctenit o matrix and containing both dispersed and massive cerb3dea. have superior corrosion resistance than the, ea oast microstructure oompieing of marteneite + auetenite + carb ,de* Presence of carbides is not detrimental to oOrrosion The effect of dispersed carbides ie governed by their size and distribution. Presence of a new phase ' (resembl ag the sigma phase f6rme'd1 on heat-treating from 105000, adversely affects' the corrosion resistance tree a. relieving has been found to be detrimental ' from the point of view Of corrosion resistance which decreases with an increase iri the test duration. iieat: treatments for producing the most useful mierostructuree have been identified„ key parameter in :c*On trolling the corrosion resistance appears to be the amount and stability of aueten te, , The results which provide useful clues to the design p future compositions, seat that there is a good possibility Of designing corrosion resistant oat irons by empto ag. the White iron route, ,.