Study On Surface Strengthening Of Deep-shovel Based On Laser Cladding Technology

With the continuous development of agricultural mechanization in China,the use of deep-shovel is increasing year by year.The traditional deep-shovel is mainly made of ductile iron,which is used as soil-engaging component part of agricultural machinery.The deep-shovel is often in contact with moist soil,especially in coastal areas of China where the air is moist,the relative humidity is high and the salt content is high,and the ductile iron is easy to be corroded.During the deep-shovel operation,,the deep-shovel is impacted by the external force,such as the stones in the soil,the Straw of crops and the corrosive stubble,Increased farming costs,shortened the service life of deep-shovel and reduced production efficiency.The titanium alloy has excellent corrosion resistance,excellent comprehensive mechanical properties and rich resources.It has a great application prospect in the manufacture and improvement of deep-shovel,but titanium alloy also has some problems such as poor wear resistance,low hardness,poor resistance to damping,and so on.There are also great restrictions on the service life of deep-shovel.In order to improve the service life of deep-shovel,the surface hardness,wear resistance and corrosion resistance of deep-shovel were enhanced by preparing high performance coating.Laser cladding technology provides a new method to improve the surface properties of materials.By high energy laser beam,a good metallurgical cladding layer can be formed between the surface and the substrate,thus improving the surface properties of the substrate obviously.In this paper,the surface of deep-shovel was strengthened by laser cladding technology to improve its surface mechanical properties and prolong its service life.In the process of laser cladding layer on the surface of deep-shovel,the input current,pulse width and scanning speed of laser cladding parameters have the most obvious influence on the dilution rate and width-height ratio of laser cladding layer.Therefore,the input current,pulse width and scanning speed are selected as the three factors of the orthogonal test,the range of process parameters is obtained through a large number of tests,and the three levels are selected for the orthogonal test,the dilution rate and width-height ratio of the cladding layer were taken as the evaluation indexes to optimize the above three parameters.The optimum parameters of laser cladding are as follows:input current is 130A,pulse width is 2.3 ms,scanning speed is375mm/min,frequency is 25Hz,The effect on the dilution rate of cladding layer is as follows:scanning speed>pulse width>input current,The influence of the width-height ratio of the cladding layer is in turn:Pulse width>scanning speed>input current.By means of scanning electron microscope and energy spectrometer（EDS）,it is found that when the mass percentage of Mg-Co-based self-fluxing alloy in cladding layer is 1:300,the base material and cladding layer have good metallurgical bonding.The dilution rate of the single-channel and single-layer laser cladding layer is calculated to be 5.12%,which is within the ideal range.The results of XRD,SEM and microhardness tester show that there are a large number of dendrites in the cladding layer,and the maximum hardness of single layer without rare earth element is862.2HV,the average hardness of the cladding layer is 3.3 times higher than that of the substrate,MgTiO₃is formed in the cladding layer without rare earth oxide,WC,Ce Mg and MgTiO₃are formed in the cladding layer with rare earth oxide,and CeO₂powder with 0.5%mass ratio is added to the cladding powder,the fusion channel is flat,the cladding layer is compact,and there are no cracks and pores.The results show that laser cladding technology can improve the surface hardness,prolong the service life,reduce the production cost and increase the economic benefit.