Research On Laser-assisted Supersonic Particle Deposition Repairing And Strengthening Process On Nickel-Based Superalloy Surface

Nickel-based superalloys have excellent high-temperature mechanical properties and high-temperature performance advantages such as high-temperature oxidation resistance,heat corrosion resistance,and ablation resistance.They are mainly used for hot-end components such as turbine vanes and guide vanes of ship gas turbines and aircraft engines.However,due to severe service conditions and high-strength use,nickel-based high-temperature parts have volume damage such as ablation,block loss,and surface damage such as abrasion,peeling,and shedding.In addition,nickel-based superalloy components are also prone to defects such as surface cracking and scratching during equipment trials.Spray repair repair coating is the main method to solve this problem.In this paper,a new process of supersonic deposition to synchronize laser irradiation and spray coating to prepare surface coatings is developed.An Inconel 718 nickel-based superalloy coating with the same composition was prepared on the Inconel 718 surface,and Cr₃C₂-NiCr cermet composite coating was prepared on the Inconel 625 surface,respectively.The microstructure,structural characteristics,anti-friction and wear resistance,high-temperature Vickers hardness,and high-temperature oxidation resistance of the coating were studied,and compared with the nickel-based superalloy matrix,the following conclusions were obtained:In this paper,starting from the process parameters of supersonic laser deposition of nickel-based superalloys Inconel 718 and Cr₃C₂-NiCr cermet composite coatings,the laser powder is used to simultaneously heat the sprayed powder particles and the nickel-based superalloy substrate,and the coating porosity,Combined strength is an important index for evaluating coating quality.The coating microstructure,structural characteristics,anti-friction and wear resistance,high-temperature Vickers hardness and resistance are studied by optimizing the coating process parameters and using various high-temperature environmental coating analysis and testing methods.The high-temperature oxidation performance is compared with the matrix of nickel-based superalloys.The experimental results were used to systematically analyze the effects of process parameters such as different laser power and different spray gun moving line speeds on coating formation.The coating parameters prepared by different processes were optimized,and a coating with a thickness of 500?m was prepared by supersonic laser deposition technology to repair and strengthen the nickel-based superalloy substrate.It provides theoretical methods and technical support for the protection and preparation of high-performance coatings in high-temperature environments equipped with nickel-based superalloy components.The surface and cross-section characteristics of coating samples prepared with different process parameters were analyzed,and the porosity of the cross-section of the coating was measured in combination with SEM backscattered electron images.The porosity of the coating decreased significantly with the increase of laser power,and the laser power was maintained.The porosity of the spray gun moving linear velocity is also decreasing.Combining the three-dimensional morphology and SEM analysis,it can be known that during the deposition of sprayed particles,the sprayed particles are accelerated to a very high speed in the supersonic spray gun and hit the nickel-based superalloy substrate,and the particles and the substrate undergo great plastic deformation and then deposit to form a coating.At the same time,the laser has the effect of simultaneously heating the sprayed particles and the substrate,further enhancing the plastic deformation ability of the two.Enhance the plastic deformation ability of the particles.The particles are flat strips in the direction of extension.Metal jets occur during the deposition of the particles.The joint between the coating and the substrate fluctuates greatly,which improves the bonding ability of the coating and the substrate.Subsequent deposited particles compact the first deposited particles and increase the compactness of the coating.Because no particles were compacted by the subsequent deposited particles,there were micro-protruding"small mountain peaks"on the coating surface.The supersonic laser-deposited coatings are mainly mechanically bonded,and there are still a small number of metallurgical bonds.The structure of Inconel 718 and Cr₃C₂-NiCr cermet composite coatings did not change significantly compared to the powder particle structure.No peaks of oxides were found by XRD analysis of the coating surface.Both coatings were not oxidized during supersonic laser deposition to achieve powder.The high temperature oxidation test of the two coatings found that during the initial oxidation of the Inconel 718 coating,the surface of the nickel-based superalloy coating was rapidly oxidized to form Ni,Fe,Cr-rich NiO,Fe₂O₃,Cr₂O₃,and spinel Cr₂O₃ containing NiO.With the extension of the oxidation time,NiO and Fe₂O₃ will form a composite phase Ni Fe₂O₄,the growth of Cr₂O₃ covering the surface of NiO will continue to expand,and a solid phase reaction between NiO and Cr₂O₃ will generate NiCr₂O₄.The oxidation products of Cr₃C₂-NiCr cermet composite coating are mainly Cr₂O₃.The high-temperature Vickers hardness of Inconel 718 coating increases with the increase of laser power.The higher the high-temperature Vickers hardness of the coating surface,the lower the gun's moving line speed and the higher the surface temperature of the deposited layer,the greater the plastic deformation capacity of the particles and the matrix,and the enhanced work hardening Increase the high temperature Vickers hardness of the coating.The high-temperature friction and wear mechanism of the coating at 250?is abrasive wear,300?is the coexistence of abrasive wear,adhesive wear,and oxidative wear,while the 350?wear mechanism is oxidative wear with adhesive wear.Inconel 718 nickel-based superalloy matrix the250,350?wear mechanism is adhesive wear and oxidative wear,and 350?is mainly oxidative wear and adhesive wear.With the increase of laser power during the deposition of Cr₃C₂-NiCr cermet composite coating,the main hard phase Cr₃C₂ in the composite coating is decomposed into Cr₇C₃,which reduces the Vickers hardness of the composite coating and leads to a reduction in high temperature friction factor.The high-temperature friction and wear volume of the coating is much smaller than that of the Inconel 625 substrate,and has excellent friction and wear resistance.The wear mechanism of the coating at 250 and 300?mainly consists of abrasive wear and adhesive wear,and the wear mechanism of 350?transitions to oxidative wear;the substrate is mainly dominated by abrasive wear at 250?and the adhesive wear and oxidative wear at 300 and 350?coexist.