Effect of Alloying Additions on the Microstructure, Corrosion Resistance and Mechanical Properties of Nickel–Silicon Alloys

Abstract

In binary nickel–silicon alloys the influence of variation in silicon content (0–15%) upon the mechanical properties and resistance to corrosion by hot sulphuric acid is correlated with the structure of the alloys. The influence of ternary additions to alloys containing approximately 10% silicon is discussed, and the beneficial effects of titanium and copper are emphasised. The improvement in mechanical properties and corrosion resistance obtained by the addition of 2–3% titanium is associated with a modification of the alloy structure. The effect of heat treatment on the structure, mechanical properties and corrosion resistance of binary and ternary alloys is discussed. The further improvement in corrosion resistance obtained by additions of titanium + copper (quaternary alloy) and titanium + copper + molybdenum (quinary alloy) is demonstrated. The mechanical properties and corrosion resistance of quinary alloys are discussedin relation to composition and alloy structure. The optimum combination of corrosion resistance and toughness was obtained with a quinary alloy containing 9·25–9·75% Si, 2·5–3·0% Ti, 2·0–3·0% Cu, and 2·75–3·25% Mo.