Tribological and electrochemical performance analysis of monolithic and multilayered titanium boron nitride thin films applied on AISI H13 steel

This study compares the microstructure, mechanical, tribological, and electrochemical performance of monolithic TiBN and multilayer TiN/TiBN coatings deposited by pulsed-DC plasma-assisted CVD on AISI H13 steel. Comprehensive characterizations were conducted, including XRD, SEM, HRTEM, AFM, nanoindentation, Rockwell C adhesion testing, pin-on-disk tribological evaluations, as well as electrochemical techniques (EIS and potentiodynamic polarization) in a 3.5 wt% NaCl solution. Findings demonstrate that both coatings form nanocomposite structures comprising TiN, TiB2, and BN phases. The multilayer exhibits refined crystallite size (12 vs. 19 nm), smoother surface topography (Ra = 4 vs. 14 nm), enhanced hardness (24.8 vs. 23.1 GPa), lower Young's modulus (272.1 vs. 318.9 GPa), and superior adhesion (HF2 vs. HF4). Tribologically, the multilayer diminishes the coefficient of friction by approximately 50–63%, narrows the wear tracks by about 77%, and exhibits a much milder wear morphology, attributed to interface-driven crack deflection and the presence of self-lubricating BN phases. However, the monolithic TiBN shows better electrochemical stability, with higher polarization resistance (5000 vs. 3500 Ω×cm2) and lower corrosion current density (1.0 × 10−5 vs. 1.7 × 10−5 A×cm−2), owing to fewer grain boundaries and an amorphous BN matrix that minimizes electrolyte ingress.