The Microstructure and Deposition Behavior of the NiCr Alloy Coating Using Laminar Plasma Spray

A new method of spraying was taken to produce both the ceramic and metal coating in the atmospheric environment. Different from the traditional turbulent one, plasma in a laminar flow state shows a much greater jet length with less ambient air engulfment. In the experiment, the total length of the plasma jet under the experiment parameter exceeded 600mm, which as well agreed with the simulation results. NiCr alloy was picked to be the coating material. The spray distance ranged from 250mm to 500mm. All the samples were observed though SEM. Coatings deposited under different stand-off distance showed different structures, which indicated that specific structure could be realized at a certain distance. Structure with higher porosity could be generated at relatively short distance and the compact structure could be obtained at a fully molten distance. The XRD patterns indicated the spraying process did not change the chemical component of the material. Besides, the linear EDS scan results indicated chemical and metallurgical bonding was realized. The Vickers hardness of the alloy coating showed a relatively high value, 8GPa. Thus, the coatings performed well and the method of laminar plasma spray was promising to generate special function and structural coatings.