Optical Monitoring in Elaboration of Metal Matrix Composites by Direct Metal Deposition

AbstractDevelopment of composites with multi-functional properties is a challenging problem that could be solved by laser cladding. The objective of the present work is to demonstrate the advantages of optical monitoring in optimizing deposition of carbide-reinforced metal matrix composites. Multi-wavelength pyrometer and infrared camera are applied to analyse high temperature heat – and mass transfer in the cladding zone. The influence of laser power, laser cladding speed and powder feeding rate on the brightness temperature are studied. The thermal images of the molten pool obtained by infrared camera for different TiC contents in the powder blend are analysed as well as the beads geometry, microstructure and microhardness

Monitoring of Single-Track Degradation in the Process of Selective Laser Melting

Selective laser melting machines provide the optimal working parameters for manufacturing during the process. However, the laser interaction with metal powder is an unstable. The gasdynamic flows make powder particles move and escape from the melt pool. This phenomenon leads to an irregular distribution of the material volume being remelted. Since the energy is constant during the process, single-tracks with different geometry are appeared and their superposition forms the 3D-object. To detect the process abnormality of stable track formation there was developed a control system based on morphological analysis of thermal image obtained by IR-camera. The temperature field distribution along the image matrix’s row with the maximum temperature was used as influencing factor on stable track formation. Roughness was reduced from 39.9 to 6.6 µm by using control system with the same process parameters. The obtained results can be applied in industrial SLM machines with the integrated active control system.Mechanical Engineerin

Study of oxygen effect on the melting pool temperature during selective laser melting

The on-line optical diagnostics studies of selective laser melting are difficult to accomplish due to the need of closed chamber of inert gas protective atmosphere. In this term, this study was initiated to make evidence of oxygen influence on the signal from the melt pool. The results make clear the temperature growth with presence of oxygen and its effect on the metallurgical contact of the single-track to the substrate. It was shown that for both used materials, the oxidation leads to an overheating but the metallographic quality differs. The experiments highlighted that the optical diagnostic means such as IR thermography camera is suitable but not sufficient solution for process control and it needs adequate evaluation. Using the track width as an approximation of the melt pool width at melting point, it was possible with some assumptions to restore the true temperature of the studied zone