| The shield machine is a tunnel boring machine that uses the shield method for construction.It has been widely used in the process of tunnel excavation.The hob ring of the shield machine is a vulnerable tool component,and the consumption of the tool is directly related to Engineering period and engineering cost,laser cladding remanufacturing technology has the characteristics of low material consumption,low coating dilution rate,small matrix deformation,and fast cooling speed.It is suitable for remanufacturing equipment under a variety of environmental conditions.Therefore,laser cladding remanufacturing technology is adopted.Cover technology to realize the remanufacturing of the hob cutter ring of the shield machine.This article focuses on the laser cladding technology,in view of the technical problems of serious wear and cracking of the hob cutter ring,the hob cutter ring material is used as the base material,and the cladding experiment is carried out,from the single-layer single-pass cladding experiment to the multi-layer wear-resistant cladding The experiment of layer and the experiment of gradient cemented carbide cladding layer are systematically studied.The main research work of this paper is as follows:(1)The influence of process parameters on the size of the single-layer single-pass cladding bath,the microstructure of the heat-affected zone,and the microstructure of the cladding layer are studied,and the single-layer multi-pass cladding is further studied.For the problem of layer overlap rate,the best powder process parameters for the base material of the hob cutter ring are obtained,which provides process parameter support for the subsequent multi-layer and multi-pass cladding layer experiments;(2)The preparation of multi-layer and multi-layer wear-resistant cladding layer was carried out,and the Ni-Cr-B and Fe-Cr-B composite coating with good metallurgical bonding was obtained,which prevented the generation of cracks and the extension from the inside to the outside.;Further study the grain morphology of Ni-Cr-B organization and Fe-Cr-B organization,especially the bonding organization between layers,the results show that Ni-Cr-B organization is better than Fe-Cr-B organization;The hardness test of the substrate and the cladding layer has been carried out,and the results show that the hardness of the cladding layer is much higher than that of the substrate,which greatly improves the surface hardness of the base material;(3)The friction and wear test of the Fe-Cr-B cladding layer was further carried out.The results show that the wear resistance of the Fe-Cr-B cladding layer material is three times that of the matrix.The friction and wear experiments under different pressures have been studied,and the results show that the greater the pressure,the greater the amount of wear.When the pressure is high,more heat is generated,which increases the temperature of the friction surface,and an oxidation reaction occurs,and severe adhesive wear occurs on the friction surface,which causes the friction coefficient to increase.(4)The preparation of graded cemented carbide was studied.For the purpose of improving impact toughness,the three powder elements of graded cemented carbide were designed with gradient distribution,and the microstructure of the cladding layer was further analyzed.Hardness test and impact toughness test and microstructure observation have been carried out.The results show that the overall hardness distribution of the graded cemented carbide cladding layer presents a gradient distribution,and a smooth internal transition is realized from the substrate to the top surface of the cladding layer,increasing step by step.The impact toughness of graded cemented carbide is the best,followed by the Fe-Cr-B cladding layer,and the impact toughness of the base material is the worst.Finally,it shows that the impact toughness of the graded cemented carbide cladding layer is higher than that of the substrate and Fe-Cr-B cladding layer.This thesis includes 54 figures,12 tables and 87 references. |
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