Ratio of Wheel/Rail Steel Hardness that Ensures Minimum Wear

Abstract

Different variants of the hardness of the wheel/rail friction pair were investigated to determine the optimal hardness range of the wheel/rail that ensures the minimum wear under selected test conditions. A pair of tests was performed on an MI-2 machine with a cylindrical wheel steel roller and a rail steel liner. The hardness of the wheel steel specimens ranged from 275 to 900 HVw. The selected of the rail steel samples of 345-455 HVr covers the possible hardness variations (350-405 HVr) of R65 type long rails produced on the standard ST RK 2432-2013 “Railway Rails Differentially Hardened and Non-heat-strengthened.” Technical Requirements. The optimal ratio of wheel/rail hardness, which ensures minimum wear due to weight loss of the tested samples, is the interval HVw/HVr–1.41-1.59. This ratio of wheel/rail hardness is practically confirmed when linear wear is determined by micrometric measurement of the impression size with HVw/HVr–1.39-1.56. The results of the laboratory tests and the suggestions for the optimal ratio of wheel/rail hardness to improve wear resistance should be verified under field conditions. Oscillography of the destruction process of plasma-hardened and non-strengthened specimens was performed to evaluate the resistance to crack initiation and propagation.

Keywords

• wheel
• rail
• hardness ratio
• plasma quenching
• crack resistance
• martensite
• troostite
• sorbite