The long time world railways practice has shown that the rail-wheel mechanical system is one of the most unique and complex systems. During transportation a variety of rail and wheel damages can take place due to service conditions, used material and technology of their production. Damage mechanisms such as wear, surface cracks, spalls, shells and elastic deformation as a result to rolling contact stresses can significantly reduce the service life of railway wheel sets and track and causing a negative impact on the rolling noise as well as on the ridding comfort. This paper presents that a proper understanding of the heating and cooling mechanisms of the wheel surface for the required hardening purpose is necessary and a mathematical model is developed to present hardening process (local heat treatment). As the material of wheel and rail is carbon steel and the heat treatment (hardening) is the most effective and efficient methods for decreasing wear on wheel sets because wheel sets are more prone to wear due to their excessive use as compare to rail or track.. The only local heat treatment is justifiable technically and economically which is applied to the most loaded working surface of wheel sets without dealing with the central part or bulk of the material. The quality of heat treatment of working surfaces of wheels is associated with the use of concentrated energy sources, such as electron and laser beam and plasma jets. This paper presents some experimental results besides the theoretical reasoning and discussions which show that the wear on the wheel sets ridges after plasma hardening is much lower (2.5 to 3 times) than the other standard heat treatments and hence due to the proper contact of railwheel the vehicle system dynamics improves as a result.
Influence of preheating parameters and local heat treatment on structure and properties of dispersion-strengthened joints of silicon-containing titanium alloys made by electron beam welding