Wear and friction losses in Indian manufacturing machinery — cutting tools, forming dies, engine components, and precision instrument bearings — represent an estimated ₹8,400 crore in annual productivity loss through unplanned maintenance and premature component replacement, according to the Confederation of Indian Industry's 2022 Tribology Benchmarking Survey. Surface engineering through physical vapour deposition (PVD) coatings offers a cost-effective pathway to extend component service life without bulk material replacement, with diamond-like carbon (DLC) coatings emerging as the premium tribological surface treatment due to their extreme hardness (2,000-3,500 HV), low coefficient of friction (µ=0.05-0.20 in dry sliding), and chemical inertness. This study systematically investigates DLC coating deposited on AISI 4140 steel substrates by magnetron sputtering PVD (argon/acetylene reactive sputtering, substrate bias −100V, deposition temperature 200°C, coating thickness 2.8±0.2 µm), comparing tribological performance against uncoated steel, plasma-nitrided, and TiN PVD-coated baselines using pin-on-disc dry sliding tribometry per ASTM G99. A Taguchi L9 orthogonal array Design of Experiment investigates the effect of four tribological parameters (sliding speed, normal load, ambient temperature, humidity) on DLC wear rate, with ANOVA and signal-to-noise ratio analysis identifying the dominant control factors. Taylor's tool life equation is established for all four surface conditions. Nanoindentation hardness profiles, XRD phase identification, and Raman spectroscopy characterise the DLC coating structure and its correlation with tribological performance.