Study On Process Parameters And Optimization And Propertis Of Arc Spraying Zinc-aluminium Coating

Arc spraying technology has the advantages of high coating bonding strength?high spraying efficiency and economical energy saving,and it is often used for the protection of large steel structures.In the marine environment or extreme harsh conditions,the corrosion resistance and wear resistance of Zn-Al coatings still need further research.In this paper,the durability,safety and reliability of engineering and equipment are improved by simulating and analyzing the arc spraying process,designing the structure of the arc spray gun,optimizing the spraying process parameters and studying th e corrosion resistance and wear resistance of the Zn-Al coating.Firstly,the characteristics of the atomized airflow field of the arc spray and the flight process of the droplets in the airflow are studieded by CFD numerical analysis method,and the influence of different spraying process parameters on the flight velocity of the airflow and the droplet is analyzed.The simulation results show that the airflow velocity reaches the maximum at the exit of the nozzle,Drastically changes up and down at the intersection of the wires,drops sharply near the substrate,and the velocity near the center of the substrate is zero.The flight of the droplet in the airflow is in a dynamic process of decelerating first and then decelerating.During the acceleration process,the droplet having a smaller diameter and a larger angle with the nozzle axis can accelerate to a maximum value within a shorter distance.During deceleration,the droplets with large diameters and small angles with the nozzle axis are not significantly decelerated.When the spray pressure is higher,the airflow and droplet flight speed are larger,and the spray distance is in the range of 120 to 180 mm,which facilitates the droplet acceleration and maintains high-speed flight.Then,by analyzing the influence of the intersection position of different wires and the diameter ratio of the nozzle on the airflow velocity,the structure of the arc spray gun is optimized.The results show that the distance between the wire intersection and the nozzle exit is reduced to 0,the airflow velocity is the largest;when the nozzle outlet to throat diameter ratio is 2,the airflow velocity is the largest.Secondly,the behavioral characteristics of droplet deposition and matrix deposition and the influence of different initial condtions on droplet deposition and solidification process were studied.The results show the smaller the initial diameter of the droplet,the shorter the deposition time and the faster the solidification,the larger the diameter of the droplet,the larger the diameter of the final spread.The greater the initial velocity,the shorter the deposition time,the more flattened,and the faster the solidification.The higher the initial temperature,the longer the deposition time and the slower the solidification.Thirdly,the influence of process parameters such as spray voltage,current,distance and pressure on the bond strength,microhardness and corrosion resistance of the coating were studied,and the process parameters were optimized by orthogonal test.It is found that the bonding strength,microhardness and corrosion resistance of the coating increase first and then decrease with the increase of spraying voltage,current,distance and air pressure.The spraying voltage,distance and voltage have the most significant influence on the bonding strength,microhardness and corrosion resistance of the coating.The optimum process parameters are: spraying voltage of 33 V,current of 200 A,distance of 150 mm and pressure of 0.7MPa.Finally,the electrochemical behaviors of Al,ZnAl alloy and Zn-Al pseudoalloy coatings in 3.5 wt.% NaCl solution were analyzed by open circuit potential(OCP),potentiodynamic polarization and EIS measurement,and their corrosion resistance was compared.The study found that ZnAl pseudo-alloy coatings have stronger corrosion resistance than ZnAl alloys and Al coatings.the wear resistance of the coating was studied by the changes of parameters such as friction coefficient,wear scar size,wear rate and wear morphology of Al,ZnAl alloy and ZnAl pseudoalloy coating.It is found that the ZnAl alloy coating has the best wear resistance,followed by the ZnAl pseudoalloy coating and the Al coating.