Volume 20, Issue 6 (November 1992)
Comparison of the Fracture Behavior of Conventional Class U Railway Wheels and an Experimental Alloy Wheel
The fracture properties of high and low carbon Class U railway wheels were compared with an experimental low carbon alloy wheel using tensile, Charpy impact, and KIc tests on specimens cut from the circumferential and transverse directions of wheel rim. The experimental alloy design was based on results of dynamometer tests and service experience that suggested a decrease in carbon content increased fracture resistance. Additional chromium was added to the experimental alloy to maintain pearlitic microstructure, thereby maintaining wear resistance. The low carbon wheels were found to have the highest fracture toughness, which was attributed to a continuous network of grain boundary ferrite that inhibited crack growth across grains. However, impact toughness was not significantly higher. Toughness of the experimental alloy was found to be similar to the high carbon wheels. However, a limited number of toughness tests coupled with a number of nonvalid tests make toughness results tentative. It was believed that the addition of chromium to produce a nearly pearlitic structure also eliminated the continuous network of proeutectoid ferrite necessary for good toughness.