A multi-sensor based online monitoring system for laser hot-wire surface cladding process

Abstract

A multi-sensor online monitoring system, including a high-speed camera, a spectrometer, and an infrared camera, was developed to enhance the laser hot wire cladding process. This innovative process feeds a preheated wire, using a hot-wire power supply, into a shallow molten pool formed on the substrate surface by a rectangular diode laser beam. This study assesses the capability of the monitoring system to detect variations in cladding process conditions that significantly influence the geometry and quality of the clad layer. Specifically, the study involved four sets of laser hot-wire cladding experiments, altering substrate surface conditions, substrate thicknesses, laser powers, and scanning speeds. The real-time data from the three sensors were synchronized and analyzed in depth, focusing on the morphology and microhardness of the clad layers. A laser vision sensor was employed to examine the surface profile and roughness of the clads. The findings indicated that the crucial role of surface preparation in influencing the dynamics of the molten pool, subsequently affecting the geometry, dilution depth, and microhardness of the clads. The sensors demonstrated increased sensitivity to changes in surface conditions compared to variations in other conditions like substrate thickness, laser power, and scanning speed. A significant correlation was found between the dilution depth, clad height, surface roughness, and microhardness of the clad layer. These correlations are in response to adjustments in laser power, scanning speed, and surface preparation and can be reliably and rapidly detected by the multi-sensor system.