Influence of Nb Reinforcement on the Wear Behavior of Spheroidal Graphite Cast Iron

Abstract

Spheroidal graphite cast iron, which is commonly used in a variety of applications, is subject to sliding wear and tear during operation. This damage can be prevented by increasing its strength value. In this study, 0%, 0.191%, and 0.304% niobium-reinforced spheroidal graphite cast irons were produced. Specimens for hardness, compression, and abrasion tests were produced in accordance with the standards for the tests of the sand mold cast specimens. In order to compare the results of the tests, test specimens reinforced with 0.191% and 0.304% niobium, as well as 0% (unreinforced), were also produced. The hardness and compression strength of the niobium-reinforced and unreinforced specimens were tested in accordance with the standards. In addition, wear tests were carried out at 5 N, 10 N, and 15 N loads for 0%, 0.191%, and 0.304% niobium reinforcements, respectively. In the hardness tests, the highest measured value was observed in the sample reinforced with 0.304% niobium, with an average of 272 HB. Since Nb is an element with high hardness, the hardness values of the samples increased with the increase in Nb reinforcement. With an average value of 1411 MPa, the niobium-reinforced sample with 0.191% niobium reinforcement exhibited the highest compression strength. When analyzing the results of the compression tests, an increasing trend was observed with increasing reinforcement ratio, as was the case with the results of the hardness tests. In the wear tests, the changes in wear volume, wear rate, and friction coefficients were examined at loads of 5 N, 10 N, and 15 N. When the test specimens with the same reinforcement ratio were examined, it was found that the wear volume loss values increased with the increase in load. As the wear resistance increases with increasing hardness value, it becomes more difficult to detach the particles from the wear surfaces. The wear volume of the samples, therefore, decreases as the hardness value increases. At the end of the experimental study, a microstructural analysis of the surfaces subjected to sliding wear was carried out. It was observed that wear marks and pits had formed on the surfaces subjected to sliding wear.