Heat treatment on nickel gunmetal

Abstract

Gunmetals are amongst the most commonly used alloys in the non-ferrous foundry. Their compositions have been standardized mainly on the basis of long experience over a limited number of alloys, rather than a systematic study of the influence of composition. The object of this thesis is to compare the mechanical properties of the three most commonly used gunmetals today, namely, LG4, LG2 and G1 (to B.S. 1400:1985), with a recently developed fully heat treatable nickel gunmetal. The original nickel gunmetal based on a composition of Cu Sn5 Ni5 Zn2, was developed in America for the production of cast components where high mechanical properties are required in conjunction with improved resistance to wear and corrosion. With the base composition, however, small additions of lead, inhibit age hardening and also promote quench cracking. These factors have given rise to production difficulties. It is believed however, that if the nickel -tin ratio is slightly modified to give more rapid ageing, this would counteract the effect of lead, and that cracking would be avoided by omitting the quenching operation during the heat treatment. The main work of the project is based on this latter nickel gunmetal - TF alloy. The nickel-tin ratio was modified to determine the optimum composition of the metal. An analysis to find the optimum solution treatment temperature, the age hardening temperature together with their respective holding time, required for this gunmetal in order to achieve the best mechanical properties in conjunction with good corrosion resistance, is carried out [...].