Formation Mechanism of Intertwining Interface in Cold Spray

Experimental investigation supported by numerical modeling was conducted to explore the formation mechanism of intertwining interface in cold spray. The result revealed that low particle impact velocity and the consequent low deposition efficiency were the essential reason for inducing intertwining interface. In addition, intertwining interface was found to generate at very beginning of coating deposition; further particle deposition posed negligible effect on the formation of intertwining interface. Based on the experimental and numerical analysis, for the first time, the formation mechanism of intertwining interface was concluded and proposed in this paper. Low deposition efficiency lead to slow coating growing rate. Therefore, at the beginning of the coating deposition, a large number of rebound particles repetitively hit the very thin single-layer or double-layer coating, forming a shot-peening effect. Such effect resulted in periodic change of plastic strain and the consequent low-cycle fatigue of the first-layer coating. Particles of the first-layer coating then fractured and mixed with the substrate material to form the intertwining structure.