Abstract: A multi-wavelengths pyrometer and an infrared camera are applied with Trumpf DMD 505 industrial-scale laser cladding machine for optical diagnostics. Brightness temperature of the molten pool is measured with the variation of the main laser cladding parameters such as scanning speed, laser power, powder feed rate and powder material composition. Black body model Micron M390 is applied to transform the raw signal from the camera and the pyrometer to the brightness temperature.
Abstract: Direct Metal Deposition (DMD) is a laser cladding process for producing a protective coating on the surface of a metallic part or manufacturing layer-by-layer parts in a single-step process. The objective of this work is to demonstrate the possibility to create carbide-reinforced metal matrix composite objects. Powders of steel 16NCD13 with different volume contents of titanium carbide are tested. On the base of statistical analysis, a laser cladding processing map is constructed. Relationships between the different content of titanium carbide in a powder mixture and the material microstructure are found. Mechanism of formation of various precipitated titanium carbides is investigated.
Abstract: Direct metal deposition (DMD) is an automated 3D laser cladding technology with co-axial powder injection for industrial applications. The actual objective is to demonstrate the possibility to produce metal matrix composite objects in a single-step process. Powders of Fe-based alloy (16NCD13) and titanium carbide (TiC) are premixed before cladding. Volume content of the carbide-reinforced phase is varied. Relationships between the main laser cladding parameters and the geometry of the built-up objects (single track, 2D coating) are discussed. On the base of parametric study, a laser cladding process map for the deposition of individual tracks was established. Microstructure and composition of the laser-fabricated metal matrix composite objects are examined. Two different types of structures: (a) with the presence of undissolved and (b) precipitated titanium carbides are observed. Mechanism of formation of diverse precipitated titanium carbides is studied.
Abstract: The results of theoretical and experimental investigations of direct metal deposition (DMD) processes involving a CO2-laser with the power up to 5 kW and wave length of 10.6 μm are presented. The physical and mathematical model of multi-layer gas flows with gas-jet transport of metal powder particles has been developed. To simulate the flows of carrier and shaping gases in annular channels of a triple coaxial nozzle, Navier-Stokes equations were applied for an axisymmetric flow. Thermodynamics and powder particles transport are calculated from a discrete-trajectory model with due regard to particle collision with solid walls of the transport nozzle. It is shown that particles may overheat on their way between the nozzle and substrate; the overheating depends on the trajectories by which particles move, on their size, and time of their retention in the laser-radiation region. The results of performed experimental researches on DMD processes visualization are presented. Some results of numerical simulation and experimental data are compared and analyzed.
Abstract: A diagnostic system based on non-intensified CCD image sensor is applied for particle-in-flight monitoring of different deposition processes: cold gas dynamic spray (CGDS), computer-controlled detonation spray (CCDS) and direct metal deposition (DMD). An additional illumination source for measuring particle velocity in CGDS and DMD processes is used. Particle velocity measurements are carried out aiming optimization of a Cold Spray nozzle with two zones of powder injection for spaying Al powder. In a pulsed-periodic process like detonation spraying, particle-in-flight visualization and velocity measurements are done by synchronizing detonation pulses with the CCD-camera-based diagnostic tool. A significant variation of particles velocity along the detonation plume is observed. In DMD process, dependence between the carrier gas flow rate and particle velocity is found.
Abstract: A physical-mathematical model is proposed for describing multi-strata flows in Direct Metal Deposition (DMD) technology with circular injection and coaxial transportation of powder. Trumpf 505 DMD machine with 5 kW CO2 laser is used in experiments. Navier-Stokes equations are written in an axisymmetric coordinate system for viscous compressible heat-conducting gas. Thermodynamics and particle transport are calculated on the base of a discrete-trajectory model. Mechanisms of interaction between multi-strata annular jets flowing out from the channels of a triple coaxial nozzle and peculiarities of a combined two-phase gas-powder jet flowing down to a plane-surface substrate are studied. Numerical simulation and experimental data are compared and analyzed.
Abstract: Direct Metal Deposition (DMD) is a laser cladding technological process for producing a protective coating on the surface of a metallic part or manufacturing layer-by-layer objects in a single-step process. The objective of this work is to demonstrate the possibility to create large-sized carbide-reinforced metal matrix composite part. Powders of Fe-based alloy (16NCD13) with different volume content of titanium carbide (TiC) are tested in experiments. Statistical analysis of the influence of main laser cladding parameters on geometrical characteristics of an individual track is carried out and regression equations are obtained. On the base of these relations laser cladding processing map is constructed. Relationships between the different content of titan carbide in the powder mixture and material microstructure are found. Mechanism of formation of various precipitated titanium carbides is investigated.
Abstract: The use of the TRUMPF 505 DMD machine with 5 kW CO2 laser allowed to scale-up laser cladding technology to an industrial level. The actual objective is to increase product quality, process stability and reproducibility. The following two original pyrometers developed by DIPI Laboratory are used: (1) 12-wavelength (in the range of 1.001 – 1.573 µm) one-spot (diameter is 800 µm) instrument with a sampling time of 50 µs; (2) monochromatic 2D pyrometer (the frame of 100 photodiodes) with a sampling time of 17 µs per one photodiode. An infra-red camera FLIR Phoenix RDASTM with InSb sensor (3 to 5 µm band pass arranged on 320x256 pixels array) with acquisition time varying from 9 µs to 16.5 ms are also employed in experiments. The variation of brightness temperature versus laser power and cladding velocity (powder Ti6Al4V) are analysed. The CCD camera based diagnostic tool was applied for on-line monitoring of particle-in-flight velocity in coaxial powder injection.
Abstract: Direct Metal Deposition is 3D material deposition process arising from laser cladding technology with co-axial powder injection. The objective of the present study is to demonstrate the possibility of manufacturing large-sized near-net-shape parts in one-step process. The metal powders of Ti (Ti6Al4V) and Fe (17-4PH, AISI 431)-based alloys are tested. Relationships between the employed DMD manufacturing strategies and strength properties of the built objects are discussed. The microstructural features of large-size laser-fabricated parts are examined. The mechanical characteristics of laser cladded material are evaluated and compared with annealed cast material. The laser-assisted manufacturing of an industrial component is presented.
