Research On Removing NiAl And NiCrAl Coatings By Plasma Spraying Technology And Properties Of Recoated Coatings

So far the plasma spraying of nial coating and nicral coating can spray a variety of materials,such as the titanium alloy and high temperature alloy,etc.In the processing of the coat spraying,frequently it happens that the basal body has tiny metallurgical defects,and the coating thickness or chemical component occur unevenness and out of limits,all of che problems maybe cause the disqualification of the coating,then affect the performance.At the same time,due to the high cost of parts processing in aviation and aerospace field,it is necessary to repair the coating,make parts reuse,repair the coating,and remove the original coating.Coating removal technology and repainting technology in parts of aero-engine parts,such as turbine blades and casing,are of great value for repairing of parts and repairing of engines.This paper about the GH4169 superalloy substrate by plasma spraying the Ni Al and NiCrAl coating,research the removal technology of two coatings.Using chemical elimination,electro-chemical method,mechanical removal method to discuss the feasibility of the method to determine the chemical method to remove the coating system feasibility,research the coating removal mechanism and removal after spraying coating bonding strength and mechanical performance i ndicators,performance evaluation of various methods on the substrate,coating mechanical effect.By the method between weight measurement and thickness measurement comparative study method to remove the coating thickness and time relationship,measure the coating removal rate and uniformity;micro expression concentration of concentration and temperature on the removal rate of the coating effect,from the reaction kinetics of simple expression removal reaction mechanism,three levels orthogonal experiment design of three factors,and screening the optimum parameters.The results showed that the higher the temperature,the higher the removal rate and the moderate removal rate.With the increase of the ion content,the reaction rate first increased and then decreased,and the removal efficiency of the solution decreased.The solution agitation can improve the uniformity of the coating corrosion,and the addition of corrosion inhibitor can make the coating removal speed controllable.Scanning electron microscopy(SEM)was used to observe the microstructure and surface morphology of the coating and GH4169 substrate.The changes of coating and matrix elements were observed by energy spectrum.The change of coating after coating removal and re spraying was studied by X-ray diffraction.The results show that choosing nitric acid as the main removal solution can effectively remove the plasma sprayed Ni Al and NiCrAl coatings on the GH4169 substrate,and basically do not cause matrix corrosion.Then,after spraying Ni Al coating NiCrAl coating adhesion properties,tensile and tensile mechanical properties,high temperature endurance performance test,the index is not reduced,at the same time again spray microstructure and first spray coating is also consistent,so the co ating thermal shock,anti-oxidation,corrosion resistance and spraying for the first time consistent,meet the targets request.Combination of aviation engine parts,and parts of the actual production process,when the coating residual amount of less than 5% of the total,can remove the residual surface coating by blowing sand method,does not affect the parts used again,considering the life and study of non spraying insulation protection method of coating surface corrosion solution for complex structural components,the protection scheme feasible,to ensure the integrity of regional surface spraying.At present,the coating removal technology has been applied to many parts processing,and the effect is good.