Simultaneous enhancement of friction and wear resistance for high‐speed braking system with Cr₃C₂‐NiCr‐coated brake disk

Abstract

The current steel brake disk and Cu‐based powder metallurgy brake pad used in high‐speed trains suffer fading coefficient of friction (COF) and excessive wear, resulting in a shorten lifetime and numerous exhausted brake disks. High‐velocity oxygen fuel (HVOF) spray‐prepared coatings have proven their ability to improve COF and decrease wear rate. In this article, Cr3C2‐NiCr coating was sprayed on a steel brake disk, and a series of emergency braking tests under dry and wet conditions were performed on a subscale brake dynamometer, to comprehensively evaluate the braking performance of coated brake disk. The results showed that the coated brake disk exhibits a higher COF at 380 km/h, which effectively inhibits the COF fade compared to the steel brake disk case. The coated brake system also achieves a lower wear rate of the brake pad at 380 km/h, showing the desired high COF and low wear rate properties of the braking system. Additionally, the coated brake disk maintained surface integrity even after severe braking tests, highlighting its potential in the braking system. Based on the characterizations of wear debris and brake pads, a harder and thinner oxide friction film plays a crucial role in achieving the excellent braking performance in coated brake disk cases.