Microstructure And Performance Analysis Of Remanufacturing Alloy Layer By Laser Cladding Of Screw Rotor Material

Twin-rotor screw compressor is widely used in industrial refrigeration,food refrigeration,air compression and other fields because of its advantages of simple structure,energy saving,high efficiency and smooth operation.The screw rotor,as the core part of the compressor,is prone to damage and failure due to its long working time in high speed,high temperature and high pressure environment.Twin screw compressor has a huge quantity in China,according to statistics,every year due to the compressor rotor scrap caused by the shutdown loss of billions of dollars,the need for effective immediate repair methods and protection measures.This study on the national natural science fund project "remanufacturing machine parts service life prediction method and experimental study(51505268)",with the support of laser cladding in the screw rotor shaft remanufacturing,microstructure and properties of alloy layer analysis for screw rotor remanufacturing repair process,remanufacturing layer microstructure and mechanical properties evaluation to provide the corresponding theoretical method and experimental data.In this paper,Ni60 alloy coating was prepared on 40 Cr matrix of screw rotor by laser cladding technique.Firstly,the laser cladding process of screw rotor material was studied.With single channel single factor experiment of laser cladding as the breakthrough point,analysis of the laser power,scanning speed,powder quantity,away from coke and other factors on the quality of the cladding layer,respectively,laws,and by orthogonal experiment method for multiple orthogonal optimized process parameters,has been clear about the factors on the impact of various factors on the quality of cladding layer and the optimal level combination,primary and secondary order to study the lap rate on the quality of the multichannel cladding layer,determine the screw rotor combination optimal technological parameters of laser cladding materials.Secondly,the microstructure and properties of remanufactured alloy layer of screw rotor shaft were studied.By means of metallographic microscope and ultra depth of field microscope,the metallographic structure of transverse and longitudinal sections of single channel cladding layer with different powder feeding amount and the microcosmic morphology of multi-channel cladding overlap zone with different overlap rates were compared and analyzed.The hardness distribution,tensile strength,fracture morphology and wear resistance of the cladding layer under optimal process parameters were tested by microhardness tester,electro-hydraulic servo universal material testing machine,scanning electron microscope and friction and wear testing machine.Finally,the remelting of laser cladding layer for screw rotor shaft is studied.In order to further reduce the porosity and surface roughness of cladding layer,laser secondary remelting was carried out on the cladding Ni60 coating surface.The effects of different remelting paths on the surface roughness,porosity and metallographic structure of the cladding layer were studied.Meanwhile,the experimental study of high-temperature friction and wear of the cladding layer and remelting layer was carried out to verify the high temperature wear resistance of the remanufactured alloy layer.