The Structure and Properties of the Alloy Cu-10Pb-10Sn-5Ni after Heat Treatment

Introduction. Lead-tin bronzes are among the most demanded materials for manufacturing parts operating under friction and wear conditions. In the majority of cases, in addition to high antifriction properties the parts should have augmented strength. However, the inclusions of lead in this material considerably decline the strength, which leads to premature failure. Despite the existing profusion of methods to improve the strength of lead-tin bronzes, some of them are hardly applicable and instable on industrial scale, while others are still experimental. Thus, the search for the techniques to increase the strength of lead-containing bronzes remains high on the agenda. The purpose of the work: studying the structure, mechanical and tribological properties of Cu-10Pb-10Sn-5Ni alloy after heat treatment on the example of Cu-10Pb-10Sn-5Ni bronze. The alloy is obtained by melting materials in a high-frequency thyristor installation in a crucible made of siliconized graphite with subsequent pouring into a metal mold. The samples are aged at a temperature of 300-500 degrees C. The methods of investigation. Mechanical tests for static tension and tribotechnical tests, as well as spectral analysis of the chemical composition and metal lographic investigations of nickel-doped lead-tin bronze are used. Results and Discussion. It is common knowledge that one of the ways to change the structure and mechanical properties of a material is heat treatment, which results in the formation of a special structure due to the dispersive decomposition after quenching and aging. The fonnation of the ordered structures during aging maximizes the hardness. It is found that the maximum value of hardness (138HB) for Cu-10Pb-10Sn-5Ni bronze is achieved by aging at the temperature of 325 degrees C for 4 hours. Aging also improves the mechanical characteristics of the samples: yield stress by 10% and tensile strength by 24%. The averaged results of the energy dispersive X-ray spectrometric analysis (EDS) of the selected phase indicate that the enlarged dispersion particles are a ternary chemical compound, presumably, Cu9NiSn3. The tribotechnical characteristics of the bronze before and after aging are investigated. It is determined that lead in bronze halves the friction coefficient. The heat treatment had no significant effect on the friction coefficient of Cu-10Pb-10Sn-5Ni bronze. The wear resistance of the bronze with lead after heat treatment is two times higher than that of the bronze before heat treatment, and five times higher than that of the bronze without lead inclusions. The presented results demonstrate the capabilities of thermal treatment in the enhancement of the strength and wear-resistance of nickel-doped lead-tin bronze.