Study On The Process And Properties Of Ni Based WC Composite Coating By Oxygen Acetylene Thermal Spraying Of Fan Blade

Fan is one of the most important auxiliary equipment in the field of energy mines.Because its use environment is bad,the corrosion and wear of blades are serious.Therefore,it is of great significance to improve the service life of the fan blades.Oxyacetylene spray welding Ni based WC is a simple,adaptable and effective device,which can repair damaged blades and improve wear and corrosion resistance,improve service life and reduce production cost.However,due to the characteristics of the equipment and process,the Ni based WC of oxyacetylene spray welding is easy to be porous,inclusion,over melting and oxidation.Based on the research of domestic and foreign scholars,this paper studies the effects of different pretreatment methods,spray welding process parameters and WC proportion.The effects of thermal spray welding on the surface deposition,microstructure,microstructure,microhardness,friction and wear resistance and corrosion resistance of the coating were analyzed.Using laser remelting and boronsiliconizing improve the coating's microscopic structure.Based on the results of experiments and tests,the following conclusions are obtained:?1?Spraying pretreatment can improve the powder deposition rate,influence of proportion: surface roughness > spraying distance > preheating temperature,the deposition rate by improved process was 43.97%.The microstructure shows that the deposition of spray powder is mainly spherical deposition and lamellar deposition.The coating is the best when the deposition is mainly lamellar.?2?The Ni based WC coating is mainly composed of g-Ni and FeNi₃,the surface hardness of NiCrBSi-35%WC is 856 HV,and the hardness reaches the maximum value of 0.2mm when the surface is about 921 HV.The content of WC is higher to the lack of Ni basic coverage protection,the surface heating effect of WC decarbonization,W distribution changes gently,while the internal WC decomposition is less,the distribution of W element to show the ladder of change,making the Cr3C2,?Cr,Fe?23C6 and?Cr,Fe?7C3 carbide increase,Si,B in peroxidation and reduce slagging in deaerator.?3?When the content of WC increased,the hardness of the coating increased,but the porosity and the inclusion of the coating increased,and the phenomenon of powder agglomeration also increased,and the pores with diameter greater than 40?m appeared in the powder agglomeration.When the content of WC is more than 35%,the wear of the coating is easy to make the hard phase particles from the whole,and the corrosion resistance is low,so that the WC particles can be separated from corrosion,and the wear resistance is better when the content of WC is 30%⁴0%.?4?The melting time is longer,the XRD diffraction peak of WC intensity is low,the more serious the decomposition,and Cr3C2 and?Cr,Fe?23C6 peak increases with the remelting time,Ni₃ B and NiSi phase peak intensity with melting time increased,the oxidation is more serious.After remelting,the friction coefficient of the coating fluctuated between 0.3⁰.6,and the average friction coefficient was 0.45 at 2 min,0.31 at 4 min and 0.28 at 6 min.The longer the remelting time is,the more smooth the surface of the coating is,the lower the porosity is,the more serious the problem is.?5?Oxyacetylene spray welding defects of NiCrBSi-WC coating are: micro pores,large pores,inclusions,uneven surface,melting and oxidation.By laser remelting modified pores,holes and inclusions reduced tightening,the coating is smooth and compact,Ni2.9Cr0.7Fe0.36 and FeNi₃ near 2q =44°of XRD peak intensity was significantly higher.?1 1 1?phase peak on crystal plane,and second strong peak of appeared 51.4 degrees and 75.6 degrees on the surface show sharp appearance.The crystal was grown in equiaxed zone and crystallinity enhancement.The thermal effect of laser makes the Cr3C2,?Cr,Fe?7C3 carbide increase,the hardness increases,the surface hardness increases to 909 HV,the average friction coefficient is reduced to 0.583.Boronsiliconizing coating Ni₃ B,NiSi boride and silicide phase increased,the friction coefficient decreased further to 0.428,the wear resistance increases 1.17 times.