Investigation of Tribological Properties of Rail and Wheel Steels
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INVESTIGATION OF TRIBOLOGICAL PROPERTIES OF RAIL AND WHEEL STEELS F. Bozkurt1 and Ü. Er2 Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 6, pp. 50 – 60, June, 2020.
The wear resistance characteristics of AISI 51B60H and 30MnB5 steels with different carbon and boron contents were investigated. The analysis of the microstructure and hardness of steels was carried out. The specific wear rates in the conditions of dry and wet friction were calculated, and the friction coefficients were determined. The worn surfaces of rail samples were studied by electron microscopy. The possibility of using boron steels instead of R260 steel, which is used for manufacturing high-speed railways, was considered.
Key words: rail wear, martensitic steels for rails, tribology of rails, boron steels.
[6, 7]. Rail wear is a critical issue in terms of service; therefore, companies make a lot of efforts to solve it. The cost of servicing a rail on a lubricant-free railway line with a capacity of 12 MGT is 54 USD per meter, and the total cost of a line 30 km long reaches about 1.5 million USD per year [8]. To reduce rail wear, the rail is made of steels with high wear resistance or heat treatment is used [9]. An important characteristic of wear processes is the friction coefficient. Friction between the rail and the wheel largely determines the values of adhesion and wear, as well as the intensity of noise generation [10]. In the dynamic simulation of train movement, as well as in the detailed calculation of the mechanics of the contact interaction of the rail and the wheel, the most important parameter is the friction coefficient Kfr . A comparison of the friction coefficients measured on the railway and in the laboratory was performed by the authors of [11]. Its values turned out to be almost similar: under conditions of dry sliding Kfr = 0.5 – 0.6, during field tests using a lubricant Kfr = 0.2 – 0.4. The friction coefficient should be optimal in magnitude. Its low value is unacceptable, as it will lead to an increase in traction efforts and the breakaway torque. The wheel–rail friction pair is an open system; therefore, many environmental factors affect adhesion. In wet conditions (high humidity or rainy weather), rail vehicles may have insufficient acceleration or deceleration due to poor adhesion in the wheel–rail contact. This causes a delay in the schedule and increases operating costs and braking length [12]. Many studies of the rail wear mechanism and the tribology of the wheel–rail contact for various test conditions have been carried out. A model with double roller
INTRODUCTION Boron steels have high hardness after heat treatment and are wear-resistant materials. They are usually used in hard operating conditions, such as mining, mineral processing and agriculture, due to their good abrasion and wear resistance. These steels have also found wide application in the automotive industry due to good deformability, low elasticity and high strength [1]. There are several publications on th
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