Relationship of the structural, mechanical, and tribological behaviors among TiCN, BCN, and CrAlN coatings in the fatigue life of AISI 1045 steel for automotive industry

This work links the relationship between the structural, morphological, mechanical and tribological behaviors with the rotary fatigue life performances of AISI 1045 steel substrates coated with titanium carbo-nitride (TiCN), chromium aluminum nitride (CrAlN), and boron carbon nitride (BCN) through physical vapor deposition. Appropriate conditions of the deposition of the coatings allowed to obtain improved properties. These coatings were deposited on AISI 1045 steel substrates. Singular layers of the different coatings were used, with a stable layer thickness of ~ 3 μm. The influence of the coating type on the crystal structure, bond energies, and microstructural properties were established by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). Mechanical properties such as hardness and modulus of elasticity of the coatings were determined by nanoindentation. Tribological characterization techniques were used to determine friction coefficients. For the rotary fatigue test, the following ratios, 70%, 65%, 60% and 55% of the ultimate stress value, were chosen to determine the applied stress levels. For all three coatings, an increase in fatigue strength was found: 9.625% for TiCN, 4.215% for BCN, and 3.954% for CrAlN. The increase in mechanical properties together with the lower presence of residual stresses in the coatings justifies the increase in fatigue resistance.