Abstract
This paper investigates the effect of high-temperature aging (600 °C and 650 °C) on the microstructure and functional properties of copper CuNi2Si alloy. The paper also presents the results of elastomeric tests performed by means of the Gleeble 3800 heat and plastic treatment simulator, as well as DTA (Differential Thermal Analysis) analysis carried out for the investigated alloy aged for 1, 2, 4 and 7 h. Corrosion resistance tests were performed by means of the potentiodynamic method with Atlas Sollich Atlas 0531 potentiostat/galvanostat in a 3% sodium chloride solution. Based on the tribological tests, it was confirmed that the CuNi2Si alloy was solution heat treated from the temperature of 1000 °C and gradually aged at the temperature of 600 °C and 650 °C for 1–7 h, characterized by a stable wear resistance. The alloy aged at the temperature of 600 °C was characterized by a lower mass loss compared to the one aged at 650 °C. Based on the DTA analysis, it was found that for the alloy aged for 2, 4 and 7 h, at the temperatures of 401 °C, 411 °C and 412 °C, respectively, the decomposition of a supersaturated solid solution took place by spinodal transformation accompanied by a sequence of phase transitions DO22 [(Cu, Ni)3Si],→ δ-Ni2Si → (Cu, Ni)3Si. The results of these investigations have proved that the CuNi2Si alloy can be widely used for electric traction. The use of alloys that replace elements made entirely of copper and, in this way influencing its lower demand, is in line with the global policy of economical management of natural resources.
Highlights
Among all the copper alloys, beryllium copper has the best strength properties, high electrical conductivity as well as resistance to corrosion and abrasion [1]
The aim of this work is to investigate the influence of high-temperature aging on the stability of functional properties, such as corrosion resistance, abrasive wear resistance as well as the influence of temperature changes on mechanical properties and phase transitions
A detailed analysis of stress–strain curves for the tested CuNi2Si alloys indicated that the deformation temperature had a large influence on the value of the flow stress, which for the applied strain conditions assumed the values from 25 to 375 MPa for the samples deformed in the temperature range from 1000 to 500 ◦C respectively and the strain rate equal to 0.1 s−1 (Figure 6)
Summary
Among all the copper alloys, beryllium copper has the best strength properties, high electrical conductivity as well as resistance to corrosion and abrasion [1]. According to European Standards [5], there are 21 grades of alloyed copper, including three with the nickel concentration of 1.3%; 2.0% and 3.5% and the silicon concentration of 0.5% to 1.2% Commercial applications of this grade of alloyed copper take advantage of its good hot and cold formability, good machinability and wear resistance. Railway electric traction (conductors or guides of section insulators) are primarily exposed to atmospheric corrosion (including, depending on the latitude, large temperature fluctuations depending on the seasons, sometimes even in the range of −40–30 ◦C) as well as chemical corrosion due to the transported materials, which are very often in the form of a cloud of dust, induced by a passing train, as well as electrochemical corrosion due to the share of the flowing electric current For these reasons, the tests of corrosion resistance using the electrochemical method seem justified. The aim of this work is to investigate the influence of high-temperature aging on the stability of functional properties, such as corrosion resistance, abrasive wear resistance as well as the influence of temperature changes on mechanical properties and phase transitions
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