In order to solve the problem that the nickel-based tungsten carbide metal composite ceramic coating with high tungsten carbide(WC)content prepared by laser cladding on the surface of nickel-based superalloy is easy to crack,the effects of different laser cladding scanning speeds(300,500,700 mm/min)and substrate preheating temperatures(ambient temperature,300 ℃,500 ℃)on the heating and cooling processes of the weld pool were investigated by using self-assembled weld pool temperature detection equipment,and the cracking mechanism of the coating was analyzed by observing the microstructure of the coating.The results show that the laser cladding parameters and coating materials will affect the cracking behavior of the coating.On the one hand,the heating and cooling rates in the molten pool during laser cladding are positively correlated with the scanning speed,but negatively correlated with the preheating temperature.Lower scanning speed and higher preheating temperature can obtain smaller temperature change rate,which is more conducive to inhibiting the overall cracking of the coating.On the other hand,because of the great difference in melting point and thermal expansion coefficient between WC and NiCrSiBC,when the cooling rate of molten pool is too high or too low,it is easy to cause WC to crack or dissociate.Therefore,it is necessary to optimize the cooling rate of the molten pool in order to effectively improve the overall forming quality of the coating.
laser claddingthermal process of molten poolceramic-metal composite coatingresidual stress
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