Microstructure And Properties Of Fe Based Coating Prepared By High Speed Laser Cladding And Remelting

As the most critical support and executive component of coal mine hydraulic support,the quality requirements of column affect the whole production process.Due to long-term exposure to high temperature,high humidity and mechanical impact,a lot of wear and corrosion on the surface of the column,and even lead to insufficient support force and instability and other safety problems,thus reducing the service life.High speed laser cladding technology is used to prepare Fe90 alloy coating with excellent performance on the worn column surface,so as to further improve the surface performance,so as to meet the requirements of column surface repair and achieve safe production.In this paper,high speed laser cladding technology is used to prepare Fe90alloy coating on the surface of 27Si Mn Steel(1)In order to obtain the best process parameters of high-speed laser cladding layer,single factor experiments were designed to study the influence of different process parameters on the heat affected zone,dilution ratio and hardness of the cladding layer.Then through the orthogonal test,the hardness and dilution ratio of the cladding layer are taken as the test indexes,and the range and variance analysis method are used to comprehensively evaluate the test results.The influence order of various factors on the quality of the cladding layer is obtained,and a group of optimal process parameters are obtained.(2)Ultra thin coating and low surface roughness are the main characteristics of macro morphology of high speed laser cladding layer.XJ-HU500 industrial microscope and vhx-6000 were used to measure the thickness and surface roughness of the cladding layer.The thickness of the cladding layer is about 200?m?400?m,and the surface roughness is controlled in the range of Ra10?Ra20.Different process parameters have different effects on it.(3)Scanning electron microscope(SEM)and X-ray polycrystalline diffractometer(XRD)were used to analyze the microstructure and phase composition of the coating.It is found that the microstructure of high speed laser cladding layer is compact,which is mainly composed of fine columnar crystals with uniform distribution,and the dendrite gap is very small.There are a few interstitial compounds with high hardness such as Fe₃B,B_305.51Si_8.44 and Mo₂BC in the cladding layer.However,for conventional laser cladding,the grains are relatively coarse and the dendrite gap is large.The surface morphology,hardness and wear resistance of high-speed laser cladding layer and conventional laser cladding layer were compared and analyzed by VHX-6000,HVS-1000 digital microhardness tester and M-2000 ring block wear tester.The results show that the surface of high-speed laser cladding layer is smooth and the roughness is low.The surface hardness and section hardness are slightly higher,and the distribution is more uniform.The average friction coefficient is low.It shows that the performance of high speed laser cladding coating is better.(4)Although high-speed laser cladding can greatly improve the cladding efficiency,the surface roughness of the cladding layer is easy to appear.Therefore,the composite technology of high-speed laser cladding and laser remelting is used to improve the surface quality of the cladding layer and further effectively improve the coating performance.The results show that the surface roughness of the coating after laser remelting is lower than that before remelting,and the microstructure of the coating is more fine and uniform.There is no phase disappearance or new phase appearance,only the phase content increases.In the aspect of properties,the hardness of the alloy increases and the wear loss decreases after remelting.Therefore,the laser remelting technology not only improves the surface quality of the cladding layer,but also effectively improves the performance of the coating.