镁合金表面AC-HVAF热喷涂Al基涂层中颗粒撞击行为与涂层组织演变机制

Particle Impact Behavior and Coating Organization Evolution Mechanism in AC-HVAF Thermal Sprayed Al-based Coatings on Magnesium Alloy Surfaces

目的探究高速空气燃料热喷涂(Activated Combustion-high Velocity Air Fuel,AC-HVAF)过程中喷涂纯铝粒子撞击基材后的状态及铝涂层的组织形态与变化。方法采用AC-HVAF热喷涂技术在AZ80镁合金基体上喷涂纯Al颗粒并且制备Al涂层,通过颗粒撞击实验获得单一撞击粒子,探讨粒子撞击形貌状态、形成原因、结合机制并分析涂层形成原因与转变结果。结果在AC-HVAF粒子撞击过程中,大功率喷枪制备铝颗粒经过短暂高温高压作用后,粉末粒子达到熔融状态,以熔融的方式撞击基体,与小功率喷枪形成的低温喷涂相比,颗粒间不再是单一机械结合。在短暂高温作用下涂层形成大量再结晶,制备的涂层获得了细小晶粒尺寸,并且形成了均匀分布位错密度,喷涂撞击形成了方向统一的织构状态。结论通过大功率喷枪制备的铝涂层在高温高压条件下使铝颗粒以熔融态撞击基体,涂层获得了更高的完整度与致密度;喷涂涂层形成了均匀细小的晶粒组织,且位错密度均匀,在受到喷涂撞击后涂层获得垂直于喷涂方向的丝织构。

The work aims to investigate the state of pure Al particles sprayed in the process of activated combustion-high velocity air fuel(AC-HVAF)thermal spraying(AC-HVAF)after the impact of the substrate,as well as the tissue morphology and changes of the Al coating.AC-HVAF thermal spraying technology was used to spray pure Al particles on an AZ80 magne-sium alloy substrate to prepare Al coatings,and a single impact particle was obtained through particle impact experiments to ex-plore the particle impact morphology,formation causes,bonding mechanisms and analyze the causes of coating formation and transformation results.During the AC-HVAF particle impact process,the aluminum particles prepared by the high-power spray gun reached a molten state after a short period of high temperature and high pressure,the powder particles impacted the sub-strate in a molten manner,and the particles were no longer mechanically bonded to each other compared with the low-temperature coating formed by the low-power spray gun.A large amount of recrystallization was formed in the coating un-der the action of the short-period high temperature,and the prepared coating acquired a fine grain size and formed a uniformly distributed dislocation density,and the spray impingement created a uniformly oriented weaving state.In conclusion;the alumi-num coatings prepared by a high-power spray gun under high temperature and high pressure conditions cause the aluminum par-ticles to impact the substrate in a molten state,and the coatings obtain higher integrity and densities;The sprayed coatings form a uniformly fine grain size organization with uniform dislocation densities,and the coatings obtain a filamentary weave perpen-dicular to the direction of the spray after being subject to the spray impacts.