The Development of High Temperature Gas Heater in the Cold Spray Coating System

It has been known that various kinds of metals and alloys can be deposited in cold spray coating process. But it is not easy to obtain dense deposits of metals such as Ti, Ni, Ta and Nb in nitrogen gas process. The deposition efficiencies are also rather low in a low temperature less than 600 ºC with nitrogen gas. Based on the fact that the critical velocity of metals or alloys in cold spray decreases as the particle temperature rises, we intended to obtain dense coatings and high deposition efficiency more than 90% even in nitrogen gas process by developing a high temperature gas heater, through which gas temperature would be heated more than 800 ºC.
We have developed the gas heater that can heat gas temperature until 900 ºC with nitrogen at gas pressure of 3 MPa. In the high temperature gas process, the deposition efficiencies of the metals increased as gas temperature rose and finally deposition efficiencies of around 90 % were obtained and the deposits were also very dense.