Powder cloud behavior in laser cladding using scanning optics

摘要

Powder feeding is one of the single most important parameters that defines a qualitative outcome of the cladding process. This study focuses on how powder feeding angle and powder carrying gas flow rate affect the powder cloud behavior in laser cladding with scanning optics. Focus of this study is to provide the knowledge on how scanned laser beam affects the powder cloud and what kind of phenomena can occur during cladding process. In this study, powder feeding angles from 40 degrees to 70 degrees were tested with powder feeding gas flow rates of 3 and 6 l/min and with laser scanning frequencies ranging from 80 to 150 Hz. Powder material used was 316L, and the substrate material was low alloyed steel. The results showed that the stability of the powder cloud was highly dependent on the tested parameters. At a steep powder feeding angle, the powder cloud under laser radiation was strongly vaporized, emitting bright visible light. However, at gently sloping powder feeding angle, the powder cloud behavior was more stable; i.e., less or no vaporization was noticed, and the emitted light was fainter. Also, a direct correlation between the vaporization of the powder cloud and the increase of dilution was noticed. It was determined to be a cause of vapor flow disturbing the powder feeding into the melt pool and thereby increasing dilution. (C) 2016 Laser Institute of America.