Gun Barrel Metallic Coating Fatigue Wear Resistance

The patent applies a composite coating structure consisting of multiple layers: a底层 layer (e.g., nickel or nickel alloy) providing corrosion resistance and bonding, an intermediate layer (e.g., cobalt-chromium alloy) providing transition properties, and a top layer (e.g., tungsten carbide or other hard coating) providing wear resistance. This composite structure allows each layer to optimize for its specific function while collectively improving fatigue and thermal resistance compared to conventional single-layer coatings.

The coating system is designed with spatially varying properties: the底层 layer has higher ductility and corrosion resistance, the intermediate layer has graded properties transitioning between底层 and top layer characteristics, and the top layer has maximum hardness and wear resistance. This local quality differentiation allows the coating to withstand thermal cycling and mechanical stresses without delamination or cracking.

The multi-layer composite coating provides a protective barrier that allows the use of high-performance propelling charges. The hard top layer resists erosion from high-pressure gases and hot propellant particles, while the ductile底层 layer absorbs thermal shocks, enabling sustained use of modern high-power charges without premature barrel failure.

The coating system acts as a protective cushion applied beforehand to the barrel bore. It absorbs and distributes the extreme thermal and mechanical stresses generated by modern propelling charges, preventing direct damage to the barrel steel and extending service life despite increased operational demands.

Instead of applying pure refractory metals directly, the patent uses composite coatings where refractory metal compounds (such as tungsten carbide, tantalum carbide) are incorporated into a metallic matrix or applied as ceramic-metal composite layers. This approach achieves comparable thermal resistance while improving adhesion to the substrate and reducing brittleness, thereby simplifying the manufacturing process.

The patent modifies the chemical composition and physical state of refractory materials by using carbides, oxides, or intermetallic compounds instead of pure metals. These parameter changes maintain high-temperature resistance while improving manufacturability through established PVD, CVD, or HVOF coating processes, reducing overall system complexity.

The patent replaces single-layer galvanic chromium with a multi-layer composite coating where the底层 layer (e.g., nickel or nickel-phosphorus alloy) provides excellent corrosion resistance through electrochemical stability and dense microstructure, the intermediate layer provides mechanical bonding and stress relief, and the top layer (e.g., hard chromium, tungsten carbide, or cobalt-chromium alloy) provides wear resistance. This composite approach simultaneously addresses corrosion and wear protection.

Each layer in the composite coating is optimized for its specific function: the底层 layer has high corrosion resistance and ductility, the intermediate layer has graded properties for stress distribution, and the top layer has maximum hardness for wear resistance. This local quality differentiation eliminates the trade-off between corrosion and wear resistance present in single-layer chromium coatings.