Characterization of laser cladding functional coatings: an in-situ monitoring and variability analysis approach

In this industry 4.0 era, additive manufacturing is proving to be a key manufacturing technology with great potential. Laser additive manufacturing-directed energy deposition, the directed energy deposition variant that utilizes metal powder, is ideal for metallic part repair and coating. It is also referred to as powder-blown laser cladding. Relatively, it is a newer additive technology that is currently attracting a lot of research. This paper uses in-situ monitoring and statistical analysis to characterize the multi-track height powder-blown laser cladding functional coating. This study investigates the effect of laser scanning speed, laser power, and shield gas flow rates on the melt pool temperature and image area. Multi-track functional coating samples are built of one layer under different shield gas flow rates and laser scanning speed levels. The powder flow rate is kept constant at its ideal level (16.2 g/min). The sensor signals, alternatively called process signatures, such as melt pool temperature and melt pool image, are gathered and used in the conducted statistical analysis to predict the process response. Multi-track height is measured after sectioning the samples. Most related work focuses on the three major process parameters: laser power, laser beam scanning speed, and powder feeding rate. A dearth of the literature considers shield gas flow rate even though it is proving significant, especially in cases with a sudden geometry change. Even though there is a shortage in functional coating (multi-track cladding) characterization, non-commercial-like scenarios such as single bead (single track) are well studied by other researchers. In-situ monitoring of the process and incorporation of sensor signals are hardly addressed for multi-track cladding. The analysis conducted in this research revealed that the shield gas flow rate, laser scanning speed, and their interaction significantly affect the functional coating’s multi-track height, melt pool image area, and melt pool temperature. Moreover, a separate experiment has been conducted to identify how the laser scanning speed and laser power affect the heating adequacy and how that relates, in turn, to the quality of the multi-track coating produced. This study paves the way for the integration of in-situ monitoring, which is rarely used in standardized commercial systems, exploring the use of process signatures in predicting the process response.