Investigation of the lubricated wear behavior of ductile cast iron and quenched and tempered alloy steel for possible use in worm gearing

Bronze-on-steel couples are commonly used in worm gearing, but alternative material combinations may provide better performance in terms of wear. Lubricated rolling-sliding tests were therefore carried out on GJS700 nodular cast iron and 42CrMo4V quenched and tempered steel. The tests were performed in the disk-on-disk configuration with the applied load, rolling-sliding ratio and lubrication selected to simulate 'in-service' severe working conditions. The tests were periodically interrupted to measure weight loss and to inspect the surface condition. At the end of the test the wear damage was studied by means of metallographic observations of the worn surfaces and the subsurface regions. Pitting damage was observed to evolve differently in the steel and cast iron specimens. Both the lubrication condition and the materials microstructure showed a strong effect on crack initiation and propagation. They influenced crack inclination and branching that resulted in the formation of pitting and spalling craters.