Properties improvement of atmospheric plasma sprayed tungsten coating by annealing

Tungsten coatings were deposited onto oxygen-free copper substrate by atmospheric plasma spraying technique. Annealing treatment was adopted to modify the inherent defects and improve the performance of the plasma sprayed tungsten coating. The effect of annealing under vacuum and hydrogen atmosphere on the properties of plasma sprayed tungsten coating was studied. The results show that the tungsten grains grow up after annealing treatment, the coatings are transformed from a disorganized structure into a columnar crystal structure with an orderly arrangement. Annealing treatment at a certain temperature can decompose and reduce the tungsten oxide in the coating into pure tungsten, thereby reducing the oxygen content and improving the purity of the coating. As a result, the thermal conductivity, microhardness and other performances of the APS-W coating are improved after annealing. •Plasma spray W coating annealing in vacuum and hydrogen atmosphere was carried out.•The coatings were transformed into a columnar crystal structure.•The tungsten oxide was decomposed and reduced into pure tungsten.•The performance of the coating has been significantly improved after annealing.