THERMAL SPRAY USING ADJUSTED NOZZLE

摘要

In a thermal spray apparatus (1) a plasma stream passes through a nozzle (2) towards a substrate (20). On entering the nozzle (2), the plasma stream passes through a plasma cooling passageway (10), to a plasma accelerating zone (11) defined by a narrowed passageway, and then into an expanded plasma/particle confining zone (12, 18) for the discharge of material from the nozzle (2). To apply thermal spray coatings (21) of increased hardness to a substrate (20), the ratio of length of the plasma/particle confining zone (12, 18) relative to the diameter of the plasma/particle confining zone (12, 18) is increased from the more conventional value to about 5:1, preferably to a ratio in the range of from 7:1 to 16.5:1. Ratios of from 10:1 to 13:1 have been found to achieve a particularly desirable result. Also the method and the coatings obtained.