Microstructure And Properties Of Laser Cladding Fe-based Coatings On 27SiMn Steel

With the development of intelligent mining in coal mines in the direction of high efficiency,green and safety,higher requirements are put forward for coal mining equipment.Hydraulic support is an important part of coal mining equipment.Long-term service in abrasion and corrosive environment,halt production or even catastrophic accidents will cause huge waste of resources and energy,and seriously threaten the life and safety of miners.Laser cladding remanufacturing is an important way to achieve professional repair and upgrade of waste products or key components.However,during the laser cladding process of the hydraulic support,the lack of wear resistance and corrosion resistance of the cladding layer and the performance degradation of the substrate near the cladding layer seriously affect the quality of the laser cladding and the service safety of the workpiece.In this paper,three Fe-based alloy powders of X1,X2,and X3 were used as raw materials,taking 27SiMn steel as the base material,using laser cladding technology,in the 27SiMn Steel surface laser clad three Fe-based alloy.the influence of powder composition on the microstructure,corrosion resistance and abrasive resistance were analyzed.and compare with electroplating chrome.By adjusting the content of Mo in the X1 cladding layer,the effect of the Mo on the microstructure,corrosion resistance,and abrasive resistance of the X1 cladding layer was explored,The effect of laser cladding thermal cycle and preheating on the microstructure and mechanical properties of 27SiMn steel in different states was explored.The main conclusions obtained in the full text are as follows:(1)The dendrite characteristics of the X1,X2 and X3 cladding layers are obvious,and the segregation degree of alloying elements is serious.The middle and bottom of the cladding layer is columnar dendrites,the top is equiaxed crystals,the trunk of the dendrites is martensite,and the dendrites are distributed with residual austenite and carbide eutectic structure.(2)The corrosion resistance of the X1,X2 and X3 cladding layers.the abrasive resistance in dry friction and 3.5wt.%NaCl are better than those of electroplated hard chromium,and the X2 cladding layer rich in Mo has better corrosion resistance.The X1 cladding layer rich in Cr has the best abrasive resistance and relatively poor corrosion resistance.(3)The content of Mo element affects the microstructure,corrosion resistance and abrasive resistance of the X1 cladding layer.With the increase of Mo contents,the dendrites in the X1 cladding layer are more developed,Mo elements segregate at the grain boundaries,and the degree of segregation of Cr elements is weakened,the content of alloy compounds increases,the carbon content of martensite and the relative The amount is reduced.(4)The addition of Mo element promotes the formation of the assassination film in the X1 cladding layer and improves the corrosion resistance of the cladding layer.With the increase of Mo content,the self-corrosion current,corrosion voltage and resistance of the cladding layer increase first and then decrease.The corrosion resistance of the 4wt.%Mo cladding layer is the best.(5)The addition of Mo element reduces the abrasive resistance of the X1 cladding layer by reducing the hardness and content of martensite.With the increase of Mo content,the friction coefficient of the cladding layer in dry friction and 3.5 wt.%NaCl continues to increase,and the wear rate continues to increase.When the Mo content is 6 wt.%,the wear rate of the cladding layer is sharp increase.(6)The hot-rolled and quenched and tempered 27SiMn cladding forms a heat-affected zone consisting of a quenched layer,a partially quenched layer and a normalized layer.The structure of the quenched layer is fine martensite,and the structure of the normalized layer is fine Ferrite and pear lite.Compared with the base metal,the tensile strength of the heat-affected zone in the hot-rolled state is increased by about 39.5%,and the elongation is reduced by about 12.5%;the tensile strength of the heat-affected zone in the quenched and tempered state is increased by about 7.5%,and the elongation is reduced by about 4.9%.(7)Preheating at 100℃～300℃ reduced the deniability of the quenched layer in the heat-affected zone of the hot-rolled 27SiMn steel,and the fracture mode of the quenched layer changed from brittle fracture to ductile fracture.As the preheating temperature increases,the relative amount of martensite in the quenched layer decreases,the relative amount of ferrite and pear lite increases,the structure becomes coarser,the hardness and strength of the heat-affected zone decrease,and the elongation decreases.Compared with the heat-affected zone that is not preheated,the strength of the heat-affected zone preheated at 100℃ is reduced by about 14.3%,and the elongation is increased by about 6.2%.