Effect of Plasma Spraying Current on Micromorphology and Properties ofCr₂O₃ Coating

Atmospheric plasma spraying technique was applied to prepare Cr₂O₃ coating on Q235B steel plate. The effect of spraying current (570-650 A) on the porosity, micromorphology, phase composition, hardness, bonding strength and wear resistance of the Cr₂O₃ coating was investigated. The results show that the porosity of Cr₂O₃ coating decreased with increasing spraying current. The porosity of the coating prepared at 650 A was the lowest of 2.18%, and the coating surface was flat; the coating and the substrate were tightly bonded, and no obvious cracks and unmelted particles appeared. The phase of the coating prepared at 570 A was Cr₂O₃, and the combination of the coating and the substrate was mechanical bonding. The coating prepared at 650 A was mainly composed of Cr₂O₃ and Cr_1.3Fe_0.7O₃, and the metallurgical bonding was formed between the coating and the substrate. As the spraying current increased from 570 A to 650 A, the microhardness of the coating increased from 1 516.23 HV to 1 760.71 HV; the bonding strength increased from 15.60 MPa to 23.60 MPa; the friction factor decreased from 0.562 0 to 0.436 9, and the wear depth decreased from 0.006 mm to 0.004 mm, indicating that the wear resistance of the coating got better.