| In order to improve the quality effect of the nickel-base alloy coating on the surface of the small modulus gear.In this paper,a processing method for sequentially processing a gear tooth top and a tooth bottom nickel-base alloy coating using a dual-channel laser was proposed.and compared with the traditional single-sided gear's surface laser cladding.The main research contents are as follows:?1?This graduation project analyzes the effects of laser process parameters on the macroscopic morphology of the cladding layer and the microstructure and elemental composition of the cladding layer of the single-pass laser cladding at different laser power densities.The experimental results show that the greater the laser power density,the larger the number and volume of columnar crystal branches inside the cladding layer,the less the intergranular structure content,the brighter white metallurgical bonding zone between the cladding layer and the substrate.Uniformity and continuity of the surface of the cladding has a cross-sectional and greatly improved the morphology changed.When the laser power density is 31.8 KW·S·CM-2,it can be seen that the pores between the metallurgical bond zone of the cladding layer and the substrate are substantially disappeared,and the bond between the cladding layer and the substrate is more firm and the transition is more natural.However,the dilution ratio of the cladding layer is large,the ablation of the top of the substrate is obvious,the depth of the substrate is deep,and the problem that the microstructure of the coating is too coarse is not well solved.?2?The reason why the nickel-based alloy coating is easy to produce cladding defects by small-mode gear's surface single-pass laser is analyzed.It can be concluded that the main influencing factor is that on the one hand,the high energy of the Gaussian heat source of the laser source is likely to cause the deep penetration of the substrate in the middle of the gear's surface to affect the microstructure of the coating.On the other hand,the small modulus gear has a special gear shape,and the top position of the gear is thin.During the processing,it is easy to excessively ablate the top position of the gear to increase the difficulty of repairing the gear shape in the later stage.Therefore,the processing idea of double-channel laser processing of small-modulus flank nickel-base alloy coating is proposed,that is,the energy of the original single-beam laser is distributed according to a certain energy ratio scheme under the condition that the total input energy of the laser is constant.On the two small spots,the tooth top position and the tooth bottom position of the gear are processed in sequence.?3?Comparing layers processed by single-pass and dual-channel laser cladding,the laser cladding process under the two 1mm spots has a certain optimization effect on the energy distribution of the original Gaussian laser source.The laser energy is concentrated in the middle part of the gear to be evenly distributed to the top and bottom of the gear in a certain energy ratio.Not only the width of the top of the substrate gear is increased from340.84?m to 460.61?m compared to the single laser cladding.,but also reduces the coating dilution rate from 34.54%to 27.28%.Secondly,the grain structure in the cladding layer processed by the two laser processes is finer than that of the single-pass cladding coating,and basically has a tendency of the thin-striped distribution.There is a metallurgical bond between the coating and the substrate,and the interior of the structure is mainly composed of crystal branches and crystal cells.The columnar crystal structure has a less obvious effect on the refinement of the structure.Finally,comparing the microhardness of the cladding layer under different processing techniques,it can be seen that the microhardness of the laser cladding coating under the two 1mm spots is higher than that of the single laser cladding,mainly due to the small precipitation of crystalline austenite containing Fe and Ni in the structure,and more Cr-rich granular cementite structure.Therefore,the overall wear resistance and strength of the cladding layer structure is better than that of a single laser cladding.In summary,the process parameters of processing a 1 mm thick nickel-base alloy coating on a 1st gear tooth surface are P=250W,u1=2.5mm/s,u2=1.67mm/s,spot diameter d=1mm,the laser power density was 31.8 KW·S·CM-2.After the double laser cladding process,the gear tooth surface has high hardness,strong pitting resistance,anti-wear and high anti-gluing ability,and meets the requirements of hard surface and core toughness. |
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