| 摘要 |
<p>Known thermal spray apparatus are modified to achieve thermal spray coatings of increased hardness. Thermal spray apparatus operate to develop a plasma stream for introduction to a nozzle, for eventual application to the surface of a substrate. Upon entering the nozzle, the plasma stream is passed through a plasma cooling zone defined by a plasma cooling passageway, to a plasma accelerating zone defined by a narrowed passageway that expands into a plasma/particle confining zone for the discharge of material from the apparatus. The narrowed passageway of the apparatus is cooled, and the powder material to be applied by the apparatus is introduced into the plasma stream along the cooled, narrowed passageway. To apply thermal spray coatings of increased hardness to a substrate, the ratio of the length of the plasma/particle confining zone relative to the diameter of the plasma/particle confining zone (the "L/D" ratio) is increased from the more conventional value of about 5:1, preferably to a ratio in a range of from 7:1 to 16.5:1, for use with coating materials including WC-Co, Cr3C2-NiCr and Cr3C2. Ratios of from 10:1 to 13:1 have been found to achieve a particularly desirable result. Also the method and the coatings obtained.</p> |
