Effects of Y 2O 3 on the microstructure and wear resistance of cobalt-based alloy coatings deposited by plasma transferred arc process

Abstract

Abstract Cobalt-based alloys with different Y 2O 3 contents were deposited on Q235A-carbon steel using plasma transferred arc (PTA) welding machine. The effect of Y 2O 3 on the microstructure and wear resistance properties of the cobalt-based alloys were investigated using an optical microscope, a scanning electron microscope (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM). It was found that a cobalt-based solid solution with a face-centered cubic crystal structure was presented accompanied by the secondary phase M 7C 3 with a hexagonal crystal structure in the Y 2O 3-free cobalt-based alloy coating. Several stacking faults exist in the cobalt-based solid solution. The addition of Y 2O 3 leads to the existence of the Y 2O 3 phase in the Y 2O 3-modified coatings. Though stacking fault exists in the Y 2O 3-modified coatings, its density increases. The addition of Y 2O 3 can refine the microstructure and can increase the wear resistance properties when its contents are less than or equal to 0.8 wt.%. However, further increase of its contents will lead to the agglomeration of undissolved Y 2O 3 particles at the γ-Co grain boundary, and will lead to a coarse microstructure and lower wear resistance properties.