Tribological Performance of Ferritic Nitrocarburizing (FNC) Treated Automotive Brake Discs

Abstract: The increase of electric vehicles in the market demands the automotive industries to search for better brake disc material with high wear resistance, corrosion resistance, and longer service life. The GCI brake discs, a traditionally used material that has less wear and corrosion resistance. So, the innovative solution to overcome the problem is Ferritic Nitrocarburizing (FNC) treatment on the GCI brake disc. The study aims to investigate the tribological behavior of the FNC-treated and untreated GCI brake discs. The three brake discs used for this study are i) Gray Cast Iron (GCI), ii) Ferritic NitroCarburized (FNC) treated GCI, and iii) Post oxidized FNC treated GCI (Corr-I-Durr) brake discs. The brake pads used in all these experiments are of Non-Asbestos Origin (NAO) material. A tribotester machine was used to investigate the tribological behavior of the brake discs, and information about the Coefficient of Friction (COF) and wear of the discs was obtained. The samples were prepared and etched to analyze the microstructures using the Scanning Electron Microscope (SEM) and Optical Microscope. The Microhardness of the brake discs is measured using the Vickers Hardness indentor. The study shows how the COF and Wear vary for different contact pressure and sliding velocities for the FNC-treated and untreated brake discs, and graphs are plotted. The COF and wear rate are influenced by the surface roughness, hardness, thickness of the compound layer, and the microstructure of the brake disc material. The compound layer which is formed during the FNC process will influence the performance of the brake discs. FNC-treated brake discs show high COF and high wear rate compared to the untreated GCI brake discs.