Optical Monitoring in Laser Cladding of Ti6Al4V
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JTTEE5 21:1357–1362 DOI: 10.1007/s11666-012-9808-4 1059-9630/$19.00 Ó ASM International
Optical Monitoring in Laser Cladding of Ti6Al4V I. Smurov, M. Doubenskaia, S. Grigoriev, and A. Nazarov (Submitted April 27, 2012; in revised form June 19, 2012) The TRUMPF 505 DMD machine with a 5-kW CO2 laser was used to enable scaling-up laser cladding (LC) to an industrial level. The aim of this study is to enhance product quality and to assure process stability and reproducibility by means of optical monitoring. Two originally developed pyrometers and an infrared camera FLIR Phoenix RDASTM are employed in the LC of Ti6Al4V powder. The variations of brightness temperature versus laser power and cladding velocity are analyzed. A CCD camera-based diagnostic tool is applied for online monitoring of particle-in-flight velocity in coaxial powder injection.
Keywords
CCD camera, infrared camera, laser cladding, optical monitoring, pyrometry, temperature measurements
1. Introduction Laser cladding (LC) is a flexible and efficient method for the deposition of diverse protective coatings (Ref 1-3). It is possible to deposit a protective coating onto a predetermined area of the specimenÕs surface subjected, for example, to severe wear conditions, or to restore locally damaged/worn-out surface. In the so-called coaxial LC, a powder flux with the desired composition is directed toward the substrate coaxially to the laser beam. Several advantages can be achieved by using a coaxial cladding head: free-directional cladding, particle-in-flight heating by laser radiation, enhanced protection of the cladded bead from the ambient atmosphere, and relatively a small heat-affected zone (HAZ) (Ref 4, 5). Robotic LC with coaxial powder injection is often referred to as direct metal deposition (DMD) (Ref 6-8). Actually, DMD technology is under intensive development. An important objective is to enhance product quality and to ensure process stability and reproducibility by significantly reducing product defects or process failure rates (Ref 9-11). The development of methods and systems for online monitoring and process control and their integration with the DMD machine is priority tasks (Ref 12-16). The objective of the present study is to demonstrate the advantages of the comprehensive optical monitoring of DMD technology applying diverse and complementary I. Smurov and M. Doubenskaia, DIPI Laboratory, Ecole Nationale dÕInge´nieurs de Saint-Etienne (ENISE), Universite´ de Lyon, 58 rue Jean Parot, 42023 Saint-Etienne Cedex 2, France; and S. Grigoriev and A. Nazarov, Moscow State Technological University ‘‘Stankin’’, Vadkovsky per. 1, 127994 Moscow, Russia. Contact e-mail: [email protected] and [email protected].
Journal of Thermal Spray Technology
optical diagnostic tools: pyrometers and an infrared camera are applied to measure brightness temperature in the molten pool and HAZ; a CCD camera-based diagnostic tool is used for the in-flight particle visualization, the particle jet stability control, and the real-time measurement of particle-in-fl
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