Monitoring of optical emissions in laser cladding of 316L stainless steel

Laser cladding is so complex that small disturbances may cause defects. Developing on-line monitoring technology for laser cladding is thus a priority task. Compared with expensive spectrometers and high-speed cameras, an economical optical sensing system based on two different photodiodes was established to optimize laser parameters and help monitor abnormal working conditions. In order to find optimal parameters, a series of experiments was carried out under different operating parameters such as laser power, scanning speed, and powder feeding rate. A practical rule is summarized to optimize process parameters by analyzing the time domain characteristics of the optical signal. Several experiments under different working conditions were performed to detect abnormal working conditions. Not only can an abnormal situation be recognized, but its type can also be distinguished by analyzing optical signals in the time and frequency domains. The optical sensing system provides a better understanding and accurate evaluation of laser cladding.