Design characteristics and development of a nozzle for coaxial laser cladding

Laser cladding by blowing powder into a laser generated melt pool is finding greater use in industry particularly with the growing interest in direct build and repair techniques currently being investigated. The process is traditionally done with a side blown powder feed. This has the limitation of not being omnidirectional. To overcome this, a coaxial powder feed system has been developed. This article describes a particular system by both mathematical models and experiment. The system has so far achieved a catchment efficiency of up to 40% with a 1 kW CO(2) laser beam. The parameters controlling this important commercial parameter are described. They include the flow structure of the powder in the beam. The control of this structure is discussed with reference to this particular coaxial flow system. (C) 1998 Laser Institute of America. [S1042-346X(98)00402-1].