<title>In-process clad quality monitoring using optical method</title>

Abstract

Although laser cladding has been accepted by industry as one of the methods for the improvement of material surface properties, it is always difficult to produce consistent products over long periods. The reason for these could be the instability of laser parameters, powder feeding parameters (when powder feeder is used) and the rise of substrate surface temperature during processing. This paper investigates the possibility of using an opto-elecironic sensor for in-process monitoring of clad quality. The experiments have revealed that clad bonding condition, clad porosity, clad uniformity (i.e. clad roughness, thickness variation and overlap consistency), substrate faults and system failure (e.g. nozzle clipping, lens cracking, powder feed failure ) etc. could be recognized by the optical signals from the melt pool radiation picked up by the sensor during processing. The use of the sensor for on-line laser cladding fault diagnostic and quality control is also discussed.