| Remanufacturing is a waste product parts as blank,and the surface of the failure parts are repaired and strengthened by advanced surface engineering technology.High velocity arc spraying and laser technology,as the common surface technology,are widely used in the remanufacturing of mechanical parts.In this paper,the 45#steel,which is commonly used in mechanical parts,was used as the substrate material,and remelting treatment of FeNiCrAl coating prepared on the substrate by high velocity arc spraying was conducted by laser technology.The parameters of remelting process were optimized by orthogonal test.The microstructure,phase composition,microhardness,fracture toughness and wear resistance of the FeNiCrAl coating before and after remelting were studied by Field Emission Scanning Electron Microscopy(FESEM),Optical Microscope(OM),Microhardness Tester,X-ray Diffractometer(XRD)and friction and wear tester.With the laser power,scanning speed and step distance as the process parameters,the porosity and the microhardness as the evaluation indexs,the parameters of laser remelting process were optimized by the orthogonal test.Laser power 1700W,scanning speed 10mm/s and step distance 2.1mm are the best process parameters by range analysis method.The laser power and scanning speed have a significant influence on the evaluation indexs of the coating by the variance analysis method.The microstructure,phase composition,microhardness and fracture toughness of FeNiCrAl coating before and after laser remelting were compared and analyzed.The results showed that the layer stack structure and pores of the spraying coating are eliminated after remelting.The microstructure of the coating becomes uniform and dense after remelting,and the coating and the substrate are changed into metallurgical bonding.The phase of spraying coating mainly include a-Fe,Cr and intermetallic compound,which include AlFe3,AlFe and Al0.4Fe0.6,and after remelting a new phase Fe-Cr and[Fe,Ni]solid solution and carbide NiCx have formed.The average microhardness of the coating after remelting is 7.79GPa,which is about 3 times that of the substrate(2.5GPa)and about 1.3 times that of the spraying coating(6.0GPa).Indentation of the spraying coating show cracks with loads on 500gf and 1000gf.The average fracture toughness of spraying coating is 1.20MPa·mI/2.Indentation of the coating after remelting did not observe cracks with loads on 300gf?1000gf.The fretting friction and wear properties of substrate,spraying coating and remelting coating were tested by the UMT-3 type multi function friction and wear tester.The effects of load on friction coefficient,wear pattern and wear amount were analyzed.The mechanism of fretting friction and wear of substrate,spraying coating and remelting coating was analyzed.The test results showed that the friction coefficient curve of substrate,spraying coating and remelting coating are divided into three stages which are the running in phase,the transition period and the stable period,and the friction coefficient value decreases with the increase of the load.The wear scar width,depth of wear and volumetric wear of remelting coating are smaller than those of substrate and spraying coating under the same load conditions,which increases with the increase of the load.The increase in remelting coating is smaller than that of substrate and spraying coating.The wear form of substrate and spraying coating are fatigue delamination wear and abrasive wear.The main wear form of remelting coating is ploughing wear.The wear resistance of remelting coating is better than that of substrate and spraying coating under the same loading condition. |
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