Research on Tribological Properties of Railroad Brake Shoes Made of Compacted Graphite Cast Iron

Since the development of railway transportation is towards the heavy duty and highspeed,the research and application of compacted graphite cast iron,which possesses the beSt thermalfatigue resistance,in railroad brake shoes composition has been done by many investigators.Yetthose research reports mainly dealt with the wear resista nce and little attention was paid to frictioncoefficient. Thus,using phosphorous compacted graphite cast irons as the testing materials,theinvestigations in this paper were systematically made on the effects of gra phite morphologies andphosphorous additions on the tribological properties in cast iron;then,based on the material'sinvestigation, the tribological properties of brake shoe s under practical working condition weremeasured.The experimental results have indicated that the compa cted graphite cast iron possessesthe best combination of wear resistance and friction coefficie nt among the different graphitemorphologies tested,thus,it is the suitable selection to making brake shoes.With the increase inphosphorous addition in compacted graphite cast iron,the friction coefficient greatly increases wtulethe wear loss obviously decreases,at the same time, the brake sparking properties were improved.The brake shoes tribological property investigations show that the material investigation is reliable.At the end of this paper,the thermal fatigue cracking tendency has been measured for different kindof brake shoes ,proving that both the crack number and crack size on friction surface of the brakeshoes ma de of phosphorous compacted graphite cast ir on was obviously diminished compa red withthat of high phosphorous greyiron,and was about the same as that of the medium phosphorous greyiron,thus,it can be concluded that phosphorous compacted graphite cast ir on brake shoes can guardthe safe running of the vehicle.