Hardness matching of rail/wheel steels for high-speed-train based on wear rate and rolling contact fatigue performance

Abstract

Hardness matching between rail and wheel is important for the safe and economic operation of high speed train. In this work, various hardness of 39.5, 36.8, 33.4, 30.5, 28.1 HRC were achieved in the wheel steels tempered at 748, 773, 793, 813, 833 K, respectively. Then the twin-disc fatigue test under 1000 MPa of Hertzian contact stress, 1676 r min−1 of rotating speed (i.e., 300 km h−1) and 0.7% of creepage was conducted using these tempered wheel steels and U71MnK rail steel with the hardness of about 32 HRC. Thus various hardness ratio of Hr/Hw (Hr is the hardness of rail and Hw is the hardness of wheel) including 0.81, 0.89, 0.96, 1.07 and 1.17 were achieved. Finally, wear resistance and rolling contact fatigue performance of the wheels as the function of Hr/Hw were evaluated and the relevant failure mechanism was discussed basing on the worn morphology and mechanical properties. The results indicated that wear rate of wheels increased with Hr/Hw. Furthermore, the wheel/rail couple presented the longest fatigue lifespan of 150 000 cycles when Hr/Hw was 0.96. Thus it can be concluded that the optimal hardness ratio of Hr/Hw was 0.96 basing on the less wear rate and the longest fatigue lifespan of the wheel/rail couples under high speed of 300 km h−1 due to the reasonable strength, ductility, toughness and hardness of the wheel steel tempered at 793 K.