Heat-treatment–enabled microstructure control and tribo-corrosion response of pulse-electrodeposited Ni–BN(h) coatings on AISI 304: A case study

Thermal processing is a practical route to tailor surface behavior in engineering components exposed to simultaneous friction and corrosion. This case study examines how post-deposition heat treatment governs the microstructure–property relationships of pulse-electrodeposited nickel coatings reinforced with hexagonal boron nitride (Ni–BN(h)) on AISI 304 steel. Coatings were heat treated at 400 °C for 1 h and oil-quenched, and their mechanical, tribological, and corrosion responses were benchmarked against as-coated (AC) counterparts. Vickers microhardness testing, tribological evaluation using a pin-on-disc setup, and electrochemical impedance spectroscopy (EIS) in 3.5 wt.% NaCl solution were performed, followed by FE-SEM examination of the wear tracks. Relative to AC coatings (371.4 HV), heat-treated (HT) coatings achieved 492.2 HV and exhibited nearly a two-order reduction in wear rate under ambient sliding (3.80 × 10 -7 vs. 2.65 × 10 -5 mm 3 /N.m). Improved corrosion resistance accompanied these changes. The enhancements are attributed to the synergistic action of BN(h)-induced solid lubrication, heat-treatment-induced formation of hardened phases including precipitation hardening and defect reduction within the nickel matrix, and carbon incorporation from SAE 40 grade oil during the quenching process, which together contribute to improved surface hardness and wear resistance. Findings demonstrate that judicious thermal treatment can deliver high-performance, environmentally benign Ni–BN(h) coatings suitable for replacing hard chrome in thermo-mechanically demanding applications.