Research On The Inner Hole Laser Cladding Head And Overlaying Property

Laser cladding on the surface of the inner hole is a new material strengthening technology.Due to the limited space inside the hole, the design of the laser cladding processing head ismore particular and difficult than the ordinary surface cladding, the light path system, claddingpowder delivery system must meet the requirements of the space environment of the innerhole surface cladding. At present, the research on the inner hole surface laser claddingprocessing head have not been seen. In this work, the inner hole surface laser claddingprocessing head and the technology of inner hole surface cladding are developed andresearched.The body structure of the inner hole surface laser cladding head is composed of opticalpath system, cooling system, powder feeding system and gas path system etc.. Themodularization structure are designed, such as the collimating mirror module, laser focusingmodule and turning module. In order to meet the requirements of the light path adjustment, theoptical system with the adjustment device are devised. The fiber laser is used with thewavelength of1070nm. The structure of Galileo inverted optical transmission system are usedbased on the special requirements of the light transmission system. The focal length ofcollimating lens is125mm, the focal length of focusing lens is300mm. The shielding gas,powder feeding gas, cooling water are applied in the laser cladding processing head.The inner hole laser cladding head are extended into the inner hole for cladding the alloypowder, the body height is61mm, defocusing amount is+35mm. The hole with the diameterabove130mm and depth within1000mm can be cladded by this head. The nominal laserpower of this head is4.0kW and can take continuous cladding processing for4hours.The processing head is used on the SUS304stainless steel surface by cladding the Cobased alloy and WC powder. With the increasing of the laser power, the microhardness of thecladding layer firstly increased and then decreased and the cladding layer microstructure isrefined when the laser power is less than4.0kW. The surface of the cladding layer is rough andthe powder materials are in the situation of incomplete fusion when the laser power is2kW.The cladding layer is got excessive heat input, the WC particles are ablated and the porositiesand cracks are appeared in the organization when the laser power is4.0kW. The dilution rate in the cladding layer increased with the increasing content of WC. When the content of WC is30wt%, the wear resistance is the best. When the content of WC is more than30wt%, the wearresistance of the cladding layer is decreased with the increasing content of WC. The optimalparameters for obtaining well cladding layer are the laser power P=3.0kW and the content ofWC is30wt%, the defocusing amount is+35mm, deposition velocity is550mm/min, thepowder delivery amount is22g/min, the shielding gas flow is20L/min and the flow of thepowder feeder is20L/min.