Abstract: Lead-bismuth eutectic (LBE) coolant in lead-cooled fast reactors can cause severe corrosion of structural materials such as fuel cladding, and surface protective coatings are regarded as one of the most promising solutions. AlCrN coatings have attracted extensive attention due to their high hardness, good chemical stability and excellent oxidation resistance, however, systematic studies on the process-structure-property relationships for nuclear applications are still lacking. The objective of this work is to develop high-performance of AlCrN coatings on 316Ti stainless steel substrates via magnetron sputtering and to clarify the optimal process window by investigating the influence of Ar/N₂ flow ratio, substrate bias voltage and deposition temperature, thereby providing a material and process foundation for future studies on coating performance under high-temperature LBE corrosion and irradiation environments. AlCrN coatings were deposited using radio-frequency magnetron sputtering with a CrAl (atomic ratio of Cr to Al is 30%∶70%) target. All substrates were mechanically polished, ultrasonically cleaned and ion-etched before deposition. Three series of experiments were designed. The first series varied the Ar/N₂ flow ratio (Ar∶N₂) from 2∶0.25 to 2∶2 at a fixed sputtering power of 200 W and bias voltage of 0 V. The second series fixed the optimized Ar∶N₂=2∶1.5 and varied the substrate bias from 0 V to −60 V at 200 W. The third series fixed the optimized Ar∶N₂ (2∶1.5) and bias (−15 V) but increased the power to 300 W and varied the deposition temperature from 100 ℃ to 400 ℃. The microstructure, phase composition, mechanical properties and film-substrate adhesion were characterized by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, nanoindentation and micro-scratch testing. The results show that Ar/N₂ flow ratio critically determines the nitridation degree and phases with a low hardness of 7.1 GPa. As the N₂ flow increases, the coating transforms into a well-nitrided structure. At Ar∶N₂=2∶1.5, the coating consists mainly of dense CrN and AlN phases, exhibits a crack-free surface and achieves a peak hardness of 26.0 GPa. The substrate bias non-monotonically influences deposition efficiency and adhesion. The deposition rate and the critical load for delamination both reach their maxima at −15 V, indicating the best adhesion strength. The deposition temperature strongly affects atomic diffusion and grain growth. At 400 ℃, the coating becomes highly dense with well-ordered equiaxed grains, and the nanoindentation hardness reaches the highest value of 28.6 GPa, far exceeding that of the bare 316 Ti substrate (about 5 GPa). In conclusion, the optimal process parameters are Ar∶N₂=2∶1.5, a bias of −15 V and a deposition temperature of 400 ℃. Under these conditions, the AlCrN coating exhibits full nitridation, a dense defect-free microstructure, strong film-substrate adhesion and outstanding nano-hardness (27.2 GPa), combining high hardness, good toughness and excellent mechanical integrity. This work establishes a clear process-structure-property relationship for magnetron sputtering AlCrN coatings and provides a solid foundation for subsequent studies on their protective performance under high-temperature liquid metal corrosion and irradiation environments.