| GH4169 is a nickel-based superalloy with excellent comprehensive performance.It is widely used in the manufacturing of complex parts in severe environment.These parts are often damaged due to various reasons,resulting in huge energy and economic losses.Therefore,the material surface shall be repaired and reinforced.Alloy element V can refine the grain and inhibit Nb segregation to some extent,so as to improve the mechanical property of cladding layer.Therefore,in this thesis,laser cladding technology was used to prepare GH4169/V cladding layer on GH2132 substrate surface,and the effect of laser cladding parameters and standard heat treatment on the structure and performance of the cladding layer prepared by this component was studied.The main contents of this thesis are as follows:（1）The effects of laser power,powder feeding rate and scanning speed rate on the microhardness,shear strength,tensile property,and tensile property of cladding layer were investigated by orthogonal test design and analysis of variance and signal-to-noise ratio,and the laser cladding process parameters was optimized based on technique for order preference by similarity to ideal solution（TOPSIS）.The results show that the laser power has a significant influence on the microhardness,tensile strength,yield strength and elongation of the cladding layer,and the scanning speed has a significant impact on the shear strength and elongation.The powder feeding rate has a significant impact on the micro-hardness and elongation.The optimal process parameters determined by the technique for order preference by similarity to ideal solution（TOPSIS）are:laser power of 2KW,powder feeding rate of 350mg/s and scanning speed of 3mm/s.（2）The microstructure,tensile fracture morphology,and shear fracture morphology of the cladding layer under different process parameters were studied.The results show that the morphology of Laves phase is influenced by solidification rate and temperature gradient,and it tends to form a long strip at the bottom of the cladding layer,while it is easier to form a granular shape at the top.Through statistical analysis of Laves volume fraction under different parameters,it is found that the precipitation of Laves phase in the cladding layer can be improved to some extent by adjusting process parameters;There are a large number of dimples on the tensile fracture surface,with the main fracture mechanism being plastic fracture.A small number of specimens can observe quasi-cleavage planes,and the fracture mechanism is a mixture of plasticity and brittleness fracture mechanism.Through the analysis of the shear fracture,it is found that dimples and smooth areas can be observed on the shear fracture surface.The smoother the overall appearance of the shear fracture surface,the greater the shear strength.（3）The microstructure,microhardness,tensile properties,shear properties and wear resistance at different temperatures of GH4169/V cladding layer before and after heat treatment were studied.The results show that heat treatment can refine the grain size and reduce the dendrite spacing.Laves phase and a few carbides and nitrides still exist in the cladding layer after heat treatment,and strengthening phase′′?′is precipitated.The precipitation of strengthening phase makes the microhardness,tensile strength,yield strength and shear strength of the cladding layer significantly improved.The rolling wear behavior of cladding layer before and after heat treatment in different temperature range was studied.The results show that the cladding layer before and after heat treatment has the best wear resistance at 600℃,and the wear rate of cladding layer before and after heat treatment is 2.5×10-5mm3/（N?m）and 2.0×10-5mm3/（N?m）respectively.There are 48 figures,29 tables and 89 references in this thesis. |
