Investigation of the mechanical properties and wear behaviour of sand cast copper nickel tin alloys

Abstract

The effect of strengthening by spinodal decomposition on the mechanical properties and the wear behavior has been investigated on cast copper-nickel-tin alloys. The investigation was performed under various conditions by varying (a) newlinenickel content from 4 to 15 wt. % while tin content is kept at 6 wt. % (b) tin content newlinefrom 4 to 8 wt. % while nickel content is kept at 6 wt. % and (c) aging temperature newlinefrom 300° C to 400° C with fixed alloy composition of Cu-5Ni-5Sn. After the casting process, the specimens were homogenized, solution heat treated and aged to induce spinodal decomposition and ordering reaction. Then, the specimens were tested / examined for (a) microstructure (b) micro-hardness (c) tensile strength, yield strength and % elongation and (d) wear rate and coefficient of friction. It was found that nickel contributes significantly to the spinodal/ordering newlineprocess whereby increasing the magnitude of the peak hardness, whereas the newlinecontribution of Sn is marginal. Both Ni and Sn contribute significantly to the kinetics newlineof the transformation whereby reducing the aging time, when either of these elements newlineis increased. The wear rate was found to be a function of hardness. The coefficient of friction is observed to be a constant (0.4 - 0.6) and independent of hardness (138 HV- 368 HV). Further, the peak hardness increases with aging temperatures up to 400° C. The yield stress and tensile stress were found to be proportional to the hardness of the newlinealloy. The percent elongation decreases with increase in the hardness. The yield stress newlineof the alloy was found to increase two times than that of traditional cast Bronze alloys.