Microstructure and corrosion resistance of iron-based amorphous coatings sprayed by plasma transfer arc

Abstract

In order to solve the serious oxidation problem of the iron-based amorphous coating by arc spraying, the iron-based amorphous coating was prepared on the 20NiCrMo substrate by plasma transfer arc wire spraying(PTWS), and the parameter optimization experiment of four-factor three-level process was designed by the response surface method, and the mathematical model relationship between argon flow, hydrogen flow, working current, spraying distance and porosity was established. Then, the iron-based amorphous coating was prepared by using the optimal process parameters, and the surface, cross-sectional morphology, phase composition and hardness of the iron-based amorphous coating were analyzed by scanning electron microscope (SEM), X-ray diffraction (XRD) and HV-1000A. The polarization properties of coating and substrate was tested by IM6ex type electrochemical workstation. The results show that the porosity of the coating will decrease with either the increase in argon gas and the decrease in spraying distance, or the decrease in argon gas and the increase in spraying distance, when the working current is constant. Under the optimal process parameters, QAr=115 L/min, QH2=4 L/min, I=300 A, D=150 mm, d=12 mm, Vwire=60 mm/s, the porosity of the obtained iron-based amorphous coating is 2.14%, the average hardness is 960HV0.1, the corrosion potential is -0.4841 V and the corrosion current was 3.716×10-5 A·cm-2, which indicate the coating has excellent corrosion resistance properties.

Keywords

• transfer arc
• wire spraying
• iron-based amorphous coating
• response curved surface