Wear Performances of Gray Cast Iron Brake Rotor with Plasma Electrolytic Aluminating Coating against Different Pads (SAE Paper 2020-01-1623)

Abstract

Gray cast iron brake rotor experiences substantial wear during braking and contributes largely to the wear debris emissions. Surface coating on the gray cast iron rotor represents a trending approach dealing with the problems. In this research, a new plasma electrolytic aluminating (PEA) process was used for preparing an alumina-based ceramic coating with metallurgical bonding to the gray cast iron. Three different types of brake pads (ceramic, semi-metallic and non asbestos organic (NAO)) were used for tribotests. Performances of PEA coatings vs. different brake pad materials were comparatively investigated with respect to their coefficients of friction (COFs) and wear. The PEA-coated brake rotor has a dimple-like surface which promotes the formation of a thin transferred film to protect the rotor from wear. The transferred film materials come from the wear debris of the pads. The secondary plateaus are regenerated on the brake pads through compacting wear debris of the pads. The wear debris is likely transported between the secondary plateaus on the pads and the transferred film on the rotor before the debris is worn off, which would reduce the debris emission. All three kinds of pads showed a similar wear rate and friction level at the room temperature testing condition. The dynamic formation and detachment of the secondary plateaus are responsible to the variation of COFs. Due to its anti-wear and anti-corrosion property, the PEA ceramic coating could be a promising solution to deal with wear, corrosion and emission issues of a brake rotor for conventional and electrical vehicles.