Nitride coatings are thin, adherent layers of transition-metal nitrides—most commonly titanium nitride (TiN), chromium nitride (CrN), titanium aluminum nitride (TiAlN), and related ternary or quaternary compounds—deposited onto a substrate to modify its surface properties without altering the bulk material ^[1]. These compounds crystallize in the rock-salt or related cubic lattice in which nitrogen atoms occupy interstitial sites of the metal sublattice, producing a strongly covalent, chemically bonded structure that combines high hardness, a high melting point, and low chemical reactivity. The deposition is conventionally carried out by physical vapor deposition routes such as cathodic arc evaporation and magnetron sputtering, in which energetic metal or metal-ion fluxes react with a controlled nitrogen partial pressure to build a dense, fine-grained film atom by atom ^[2]. Because the coating and substrate possess different coefficients of thermal expansion, the as-deposited layer typically retains residual compressive stress, which must be managed together with grain morphology, composition gradients, and multilayer architecture to suppress crack initiation and delamination ^[3]. Functionally, nitride coatings constitute a surface system in which the nitride phase acts as a hard, wear-resistant and oxidation-resistant barrier while the underlying metal or cemented-carbide substrate supplies toughness.