Study Of Forming Mechanism And Properties Of Improved Copper-Based Alloy Fabricated By Laser Deposition In Underwater Environment

Underwater online repair technology can provide timely and effective maintenance support for damaged marine engineering parts.In the field of underwater repairing,laser deposition technology has shown great application prospects due to its incomparable technical advantages.However,due to the development of underwater laser deposition repair technology is still in its infancy,the theory and experience can be used for reference are little.The water environment has greatly increased the complexity of the laser deposition process,thus,development of integrated underwater laser deposition repair theory is of great importance.Therefore,this paper will start from clearing interaction between laser,water and Cu alloy,comprehensively evaluates the influence of the interaction of the three on the forming quality of laser sedimentary layer,reveals the key influencing factors of the quality of laser sedimentary layer under water environment,and specifically designs protective coating and clarifies its protective effect.Explores the laser melting pool surface tension on the quality of the deposit forming,clear about the relationship between the forming quality and the surface tension and surface curvature radius of sediments and sediment,thereby provides certain theoretical guidance and techni cal support to Cu alloy structure in the water environment of the laser online repair.Through theoretical calculation,it is found that the liquid water on the surface of NAB coating with different radius of curvature has different vaporization phenomenon.Water on the surface of NAB laser deposited coating with small radius of curvature is more likely to form violent boiling phenomenon.Due to the interaction between laser,water and metal target,plasma will be generated,which will induce cavitation effect,and cavitation bubble will generate high-speed water jet at the moment of collapse.These factors are all unfavorable to the laser deposition process.In order to improve the forming quality of Cu alloy coatings,these factors need to be effectively controlled,including minimizing the content of water in the laser processing area,moderately increasing the curvature radius of the surface of the coatings,moderately improving the strength of the material melt and the impact resistance of the surface,and reducing the introduction of harmful impurities.By introducing gasification cladding,the forming quality of NAB coating fabricated in water environment is greatly improved.Gasification cladding decomposes under the action of laser irradiation and generates enough CO2.Studies have shown that CO2 is difficult to be ionized.Therefore,gasification cladding plays an important role in creating atmospheric conditions in the process of laser deposition in underwater environment.The hard ionized gas in the gasification cladding has a good maintenance effect on the laser beam channel,and the metal plasma has a good promotion effect on the formation of the NAB laser deposited coating.By analyzing the surface characteristics of Ti-rich NAB laser deposited coating,it is found that the higher the Ti content is,the higher the surface tension will be.In addition,due to the interaction between gaussian beam and prepalced powder coating in the processing process,the curvature radius of the surface of NAB sediments with high Ti content increases.The surface of the hot arc with a large radius of curvature has a weak steamization behavior,and the impact caused by the generation and rupture of the steam bubble is small.On the other hand,the melting pool with greater surface tension has stronger impact resistance,so the coupling of these two factors can greatly improve the forming ability of NAB laser deposited coating.Rare earth elements and CaF2 were further introduced into laser-deposited materials in order to regulate the formation of microstructure and reduce defects.Among them,the introduction of rare earth elements enhanced the diffusion effect of various elements in the Ti-rich coatings,so as to make the structure of the elements distribution more uniform.The rare earth elements enriched near the grain boundary,which enhanced the corrosion resistance of the sediments.CaF2 reacts with hydrogen to generate HF gas which is insoluble in metal liquid,thus reducing the content of H in the coatings.In addition,the presence of F element and rare earth element can increase the film formation rate of the surface passivation film in the electrochemical corrosion process.Therefore,the corrosion resistance of the coatings is significantly improved under the coupling effect of rare earth and CaF2.In addition,the wear and abrasion resistance of the coatings under atmospheric conditions and high cl-water media is improved due to the lubrication effect of fluoride on the surface of the coatings.