Effect Of Acoustic Field On Microstructure And Properties Of Ni-based Alloy Coating Prepared By Plasma Spraying

Plasma spraying technology is widely used in aerospace,ship,automobile,energy,electronics and other high-end technology fields because of its high spraying temperature,simple operation,accurate control of process parameters,good reproducibility,etc.Controlling the wetting and solidification process of the droplet on the substrate surface can effectively control the microstructure and properties of the coating in the process of plasma spraying deposition.The acoustic field can promote the wetting of the material and affect the solidification process by its sound pressure,sound flow effect,mechanical effect and thermal effect.In this study,the acoustic field and plasma spraying technology were combined to prepare NiAl10 coating by controlled variable method.The optimum spraying process parameters of NiAl10 alloy coating are determined from the surface deposition morphology,thickness and the number of defects of the coating.The effects of different frequency low frequency acoustic field and different power ultrasonic field on the micro structure and properties of NiAl10 alloy coating prepared by plasma spraying were studied without changing the composition of spraying material and spraying process parameters.The results show that:(1)The optimum process parameters for preparing NiAl10 coating by plasma spraying are as follows: spraying current 500 A,spraying distance 150 mm.(2)Under the mechanical vibration effect of the low-frequency sound field,the droplet spread evenly,and the reduction of the drop fluctuation makes the lamellar structure combine closely.Compared with the NiAl10 coating without adding sound field,the porosity of the coating decreased by 12.6%,30.1%,22.0%,and the micro hardness of the coating increased 14.6%,30.5%,20.1% at 100 Hz,300 Hz,and 500 Hz,respectively,and the micro hardness of the coating increased by 14.6%,30.5% and 20.1%,respectively.The tensile bonding strength of the coating was increased by 44.1%,108.4% and 69.4% respectively.Under the action of high energy ultrasonic field,the gap between lamellar structures decreases and the bonding between coating and substrate is improved.Ultrasonic field can refine and disperse the gas entrapped in the spray coating process,inhibit the formation of large pores and reduce the porosity of the coating.Compared with the samples without ultrasonic field,the porosity of the coating decreases by 11.4%,respectively.40.9%,30.1%.The micro hardness of the coating increases by 16.0%,33.0% and 31.6% respectively.The tensile bonding strength of the coating was increased by 40.3%,119.2% and 78.9%respectively.