Ultra-high-speed laser material deposition for internal surfaces

Abstract

Due to the limited access, Laser Material Deposition (LMD) on internal surfaces, i.e. for the repair or coating of cylinder sleeves, bearings and housings of the oil-and gas industry or plastic and extrusion components is particularly challenging. For this purpose, various LMD processing heads for different inside diameters and immersion depths have been developed and are used in industry. However, for many applications the feasible layer thicknesses of LMD (> 500 µm) are too large and attainable coating rates (coated area per time) in the range of 10-50 cm2/min are far too small for the processing of large components. With the recently developed ultra-high-speed LMD, much thinner, pore-and crack-free layers with a thickness in the range of approx. 10-250 µm can be deposited with coating rates up to 500 cm2/min on the outside diameter of cylindrical parts. For this process variant, the size of the powder focus plays a crucial role, having a decisive influence on the achievable deposition speed, the dilution as well as the quality of the produced layer. Up to now, the required small powder focuses (0.5-1 mm) can only be produced with continuous coaxial powder feeding nozzles. On the account of the restricted access, so far only discrete coaxial or lateral powder nozzles are used for internal LMD processing heads, which are not applicable for ultra-high-speed LMD.In the present paper a specially designed continuous coaxial powder nozzle for an inside LMD processing head is introduced. With the new system technology, the ultra-high-speed LMD approach is adapted for the processing of internal surfaces. Inconel 625 (IN625) is deposited with coating rates up to 200 cm2/min and powder mass flows of up to 25 g/min. The influence of the coating rate as well as the powder mass flow on the layer thickness is investigated. With the novel system and process technology, pore-and crack-free wear and corrosion protection layers with a thickness in the range of approx. 50-350 µm can be deposited inside tubes with a minimal inside diameter of 100 mm.Due to the limited access, Laser Material Deposition (LMD) on internal surfaces, i.e. for the repair or coating of cylinder sleeves, bearings and housings of the oil-and gas industry or plastic and extrusion components is particularly challenging. For this purpose, various LMD processing heads for different inside diameters and immersion depths have been developed and are used in industry. However, for many applications the feasible layer thicknesses of LMD (> 500 µm) are too large and attainable coating rates (coated area per time) in the range of 10-50 cm2/min are far too small for the processing of large components. With the recently developed ultra-high-speed LMD, much thinner, pore-and crack-free layers with a thickness in the range of approx. 10-250 µm can be deposited with coating rates up to 500 cm2/min on the outside diameter of cylindrical parts. For this process variant, the size of the powder focus plays a crucial role, having a decisive influence on the achievable deposition speed, the diluti...