Tiwari N, Sahasrabudhe S N, Tak A K, Barve D N, Das A K
Laser & Plasma Technology Division, Bhabha Atomic Research Centre, Trombay 400085, India.
Rev Sci Instrum. 2012 Feb;83(2):025110. doi: 10.1063/1.3675887.
A high speed camera has been used to record and analyze the evolution as well as particle behavior in a single wire arc plasma spray torch. Commercially available systems (spray watch, DPV 2000, etc.) focus onto a small area in the spray jet. They are not designed for tracking a single particle from the torch to the substrate. Using high speed camera, individual particles were tracked and their velocities were measured at various distances from the spray torch. Particle velocity information at different distances from the nozzle of the torch is very important to decide correct substrate position for the good quality of coating. The analysis of the images has revealed the details of the process of arc attachment to wire, melting of the wire, and detachment of the molten mass from the tip. Images of the wire and the arc have been recorded for different wire feed rates, gas flow rates, and torch powers, to determine compatible wire feed rates. High speed imaging of particle trajectories has been used for particle velocity determination using time of flight method. It was observed that the ripple in the power supply of the torch leads to large variation of instantaneous power fed to the torch. This affects the velocity of the spray particles generated at different times within one cycle of the ripple. It is shown that the velocity of a spray particle depends on the instantaneous torch power at the time of its generation. This correlation was established by experimental evidence in this paper. Once the particles leave the plasma jet, their forward speeds were found to be more or less invariant beyond 40 mm up to 500 mm from the nozzle exit.
一台高速摄像机被用于记录和分析单丝电弧等离子喷涂炬内的演变过程以及颗粒行为。市售系统（如Spray Watch、DPV 2000等）聚焦于喷涂射流中的一个小区域。它们并非设计用于跟踪从喷枪到基材的单个颗粒。使用高速摄像机，对单个颗粒进行了跟踪，并在距喷枪不同距离处测量了它们的速度。距喷枪喷嘴不同距离处的颗粒速度信息对于确定正确的基材位置以获得高质量涂层非常重要。图像分析揭示了电弧附着到金属丝、金属丝熔化以及熔融物从尖端分离的过程细节。针对不同的送丝速度、气体流量和喷枪功率记录了金属丝和电弧的图像，以确定兼容的送丝速度。利用飞行时间法，通过对颗粒轨迹的高速成像来确定颗粒速度。观察到喷枪电源中的纹波会导致输入到喷枪的瞬时功率有很大变化。这会影响在纹波的一个周期内不同时间产生的喷涂颗粒的速度。结果表明，喷涂颗粒的速度取决于其产生时喷枪的瞬时功率。本文通过实验证据建立了这种相关性。一旦颗粒离开等离子体射流，发现它们在距喷嘴出口40毫米至500毫米的范围内，向前速度大致不变。
