高速电弧喷涂雾化熔滴传热过程数值分析Ⅱ.工艺参数对熔滴传热过程的影响

在高速电弧喷涂雾化熔滴传热过程数学模型的基础上，用Fe-Al合金进行了数值计算，分析了工艺参数对熔滴传热过程的影响。结果表明，熔滴尺寸越小，在一定喷涂距离上的对流换热系数则越大、熔滴温度越高、固相分数越小、冷却速度越大；雾化气流压力和喷涂电流越大，在一定的喷涂距离上熔滴温度也就越高，熔滴中的固相分数越低，且其凝固过程也越长；熔滴的冷却速度对熔滴尺寸和喷涂距离的变化十分敏感，而对雾化气流压力和喷涂电流的变化不太敏感；Fe-Al合金熔滴的液态冷却速度达10^5～10^7K／s数量级，预示涂层将具有快速凝固组织特征。

Numerical analysis of heat transfer behavior of atomized droplets during high velocity arc spraying: Ⅱ Influence of process parameters on heat transfer behavior of droplets

The influences of several important process parameters on the heat transfer behavior of the atomized droplets were numerically simulated and analyzed. The results show that the process parameters such as atomizing gas pressure, spraying current and spraying distance have great influences on the heat transfer behavior of the droplet. The droplet size considerably affects the heat transfer behavior of the atomized droplet. To a certain spraying distance, decreasing droplet size will increase the convective heat transfer coefficient, temperature and cooling rate, and decrease the solid fraction. Increasing atomizing gas pressure and spraying current will increase the droplet temperature and decrease the solid fraction to a certain spraying distance, and also extend the solidification process to a larger spray distance. The droplet cooling rate are much sensitive to the droplet size and spraying distance, but insensitive to the atomizing gas pressure and spraying current. The initial cooling rates of different size droplets range from 105 K/s to 107 K/s, thus producing the coating microstructure with the features of rapid solidification.