Corrosion and wear behavior of AISI 4140 brake discs in simulated drilling environments

Abstract Brake discs in drilling rig drawworks are exposed to harsh environmental conditions, including saline fluids, corrosive vapors, and mechanical wear under heavy loads. These factors can significantly reduce corrosion resistance and degrade tribological performance, both of which are critical for ensuring safe and reliable braking during drilling operations. This study examines the corrosion and wear behavior of AISI 4140 steel brake discs in combination with phenolic resin-based brake pads. The disc material was subjected to three simulated environments at room temperature: NaCl immersion, NaCl vapor, and HCl vapor. The highest corrosion rate occurred in NaCl immersion (0.1366% mass loss), followed by NaCl vapor (0.0365%) and HCl vapor (0.0230%). Surface degradation was confirmed through roughness measurements and visual inspection, with the most severe deterioration observed under NaCl immersion. Friction performance, assessed using pin-on-disc tests, showed that NaCl vapor exposure reduced the coefficient of friction, while HCl vapor led to a slight increase, likely due to pitting and surface hardening effects. These findings suggest that chloride-induced corrosion weakens the friction interface, whereas acidic vapors alter surface chemistry, influencing friction behavior.