The Quality Testing And Property Analysis Of Remanufactured Parts By Laser Cladding

With the promotion of urbanization and implementation of the Belt and Road strategy in our country,the demand for construction machinery is increasing day by day.Most of them are damaged for surface abrasion and corrosion of 42 CrMo core components.In order to extend their service life,improve their performance and achieve a green circular ecnomy,this article focus on the remanufacturing of laser cladding stellite6 coating on 42 CrMo surface.(1)Firstly,this artcle studies single stellite6 coating on 42 CrMo and then analyzes the effects of laser power,scanning speed,powder feeding speed,spot diameter on dilution ratio as well as microhardness of single cladding layer and the interaction among the main influencing factors by orthogonal test.It can be observed that laser power is the greatest factor for the dilution ratio of the cladding layer.Nevertheless,for the microhardness of the cladding layer,the scanning speed is the greatest factor.Based on the evaluation of the dilution ratio and microhardness of the cladding layer,the optimal combination of process parameters can be achieved,which is laser power 1100 W,scanning speed 8mm/s,powder feeding rate 1.2~1.4rad/min,and spot diameter 3.7 mm.(2)Secondly,the surface friction and wear properties of multi-pass lap cladding coatings are studied based on the combination of single-pass cladding process parameters.The wear pattern between multi-pass overlapping stellite6 coating and GCr balls reciprocating linearly as well as the wear mechanism of different overlapping ratios are investigated.It’s obviously that the wear forms of the coating are abrasive wear and fatigue wear.The wear resistance of the coating increases with the increase of the overlap ratio,while the reinforcement is gradually decreased.It is attributed to the increase of overlap ratio,the powder melts more fully in the early stage,the content of carbon-containing hard phase in the lapping area of the coating increases rapidly.Accordingly,the microhardness and wear resistance of lapping area are enhanced.In the later stage,owing to the excessive laser energy density,the CoC2 phase in the carbon-containing hard phase will be decomposed which results in a slow enhancement of the wear resistance.(3)Thirdly,based on the combination of single-pass cladding process parameters,it not only explores the corrosion process of multi-pass overlapping cladding coating in 3.5%NaCl electrolyte solution,but also studies the influence mechanism of different overlapping ratios on the corrosion resistance of stellite6 cladding coating surface.The results show that the corrosion of the coating can be divided into three stages as followings.The first stage is that the electrolyte solution gradually permeates into the inner substrate through defects,such as pores or cracks on the surface of the coating and so on.And the corrosion channel is formed by disintegrating the(Cr,Fe)7C3 phase inside,which belongs to a pore corrosion in local corrosion.In the second stage,the electrolyte solution contacts the 42 CrMo matrix through the coating so that the coating and the matrix form a primary cell rapidly corroding the matrix,which is a crevice corrosion in local corrosion.In the third stage,the accumulation of corrosion products on the surface of the substrate forms Fe2O3 oxide film,which slows down the corrosion degree of the substrate to a certain degree.In addition,with the increase of the overlap ratio,the corrosion resistance of stellite6 coating firstly increases and then decreases,resulting from the more sufficient remelting,the high internal density and the excellent corrosion resistance of the coating.In the later period,due to the high laser energy density and the excessive internal thermal stress in the remelting zone,cracks and pores increases,resulting in the electrolyte solution penetration to be intensified and the corrosion resistance of the coating to be weaken.(4)Finally,a mathematical model of rapid stratification planning for multi-channel and multi-layer overlapping cladding is established.According to the reasonable process parameters,multi-pass overlap ratio and geometric size of the repaired area,a theoretical basis for the rapid delamination planning of multi-channel and multi-layer overlapping cladding is provided.It is exceedingly significant for large-scale and rapid remanufacturing of damaged 42 CrMo components,thus improving the remanufacturing efficiency of 42 CrMo damaged parts.