In large industrial applications, strong demands are required on materials to improve production capacity and efficiency. Improvement of damage and loss of function of a component, surface modifications or coating technologies are often applied . Plasma spraying is one of several methods of coating. Plasma spraying involves generating a plasma jet using a plasma spray gun with a tungsten cathode. The coating material, such as metal or ceramic, is heated to close to melting, accelerated in the plasma jet, and sprayed onto the base material. Thorium oxide-containing tungsten is generally used for the cathode electrode. However, thorium is radioactive; therefore, a material that does not contain thorium and has better erosion resistance than thorium-containing tungsten is required .
In the present study, we used neodymium oxide-containing tungsten as an alternative for thorium oxide-containing tungsten. Neodymium oxide-containing tungsten contains no radioactive substances, and can be used in plasma torches as the cathode for the DC arc. We evaluated the performance and erosion mechanisms by measuring the surface temperature of the electrode. We used a bandpass filter (BPF) optical system that transmits only specific wavelengths.