| Q235steel is one of the most common low carbon structural steel, It has the advantageof low carbon content, good strength, good toughness and weld ability and low cost. So it iswidely used in construction engineering structure. Such as the material of Q235plate ismainly used in construction engineering and bridge structures. In the actual workenvironment, steel plate will suffer from medium corrosion and load impact, so it willproduce the phenomenon of corrosion and wear. In order to improve its surface structure andimprove the surface performance, this topic mainly using laser cladding technology lasercladding316L coating and316L/Al2O3composites coatings which can improve the wear andcorrosion resistance of Q235steel.The laser cladding technology is applied on the surface of Q235steel to laser316Lcoating,316L/Al2O3composite coatings. Exploring the morphology and the size of crosssection in single factor experiment of single channel316L coating；Obtaining the bestparameters by using the orthogonal experiment. Studied the quality of cladding layer formingunder the different scanning interval；Analyzed cladding layer interface morphology whichunder the different scanning speed and laser power. Different microstructure and phase ofcladding were analyzed; Tested the hardness of different cladding layers, wear resistance andcorrosion resistance. Finally, analysis the causes of defects in the cladding layer, And toreduce the cladding layer ball, cracks, holes and other defects inclusion proposed appropriatemeasures. The results showed that:(1) Width, height and depth of the single-channel laser cladding are increased as theincreasing of current, laser pulse width and frequency. while are gradually reduced with theincrease of the scanning speed. When the process parameters: current is160A, the scanning speed of110mm/min, the laser pulse width of4.0ms, a pulse frequency of10Hz, claddingsurface without cracks, porosity, inclusions and other defects, Also achieved a goodmetallurgical bond.(2) The organization which from the bottom to the upper cladding layer are flat crystal,columnar crystals, cellular crystal, and finally to the dendrites. When the content of Al2O3is6%, the organization of composite coating is small. When the content of Al2O3powder ismore than6%, the cladding layer will appear white part which is not dissolved Al2O3particles, Thus, cladding layer will have a lot of holes, resulting in deterioration of the qualityof cladding layer316L powder phase is austenite phase, while the316L and316L/Al2O3coating increase the ferrite phase.(3) The hardness of316L stainless steel cladding layer is about230-270HV, the averagecoefficient of friction is as low as0.3608, and the wear loss is0.00875g;316L+6%Al2O3coating is about568HV, the average coefficient of friction is0.1246,and the wear loss is0.00007g;while the hardness of the Q235substrate is only between110-140HV, the averagecoefficient of friction is0.4213,and the wear loss is0.01226g. Compared to the substrate, thehardness and wear resistance of316L coating is slightly improved. While316L/Al2O3coatingsignificantly increased. From the wear mechanism, the substrate Q235steel and316Lcoatings are the form of abrasive wear and adhesive wear. While the316L/Al2O3compositecoatings are mainly abrasive wear.(4) Electrochemical corrosion and salt spray test measurements show: The corrosionresistance of316L coating is much improved than the substrate, in the316L/Al2O3coating,when the content of Al2O3exceeds6%, the corrosion resistance of the cladding layer weredecreased. Generally speaking, the corrosion resistance of316L/Al2O3composite coating isbetter than the Q235steel. |
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