Influence of Y₂O₃ Content on Microstructure and Properties of Laser Alloying WC/Ni Metal Ceramic on 38CrMoAl Steel

Abstract

WC/Ni reinforced layers with different Y2O3 contents were fabricated on the surface of 38CrMoAl steel by laser alloying. The influence of Y2O3 content on the phase composition, microstructure, microhardness and tribological performance of the alloying layers were investigated via X-ray diffraction, scanning electron microscopy, electron microprobe, Vickers hardness tester and friction wear testing machine. The results show that the alloying layers with different Y2O3 contents all consist of γ-(Fe, Ni), martensite matrix, M3C, and WC phases. Nano-WC particles are mainly distributed between the dendrites in the top of the alloying layers, while the micro-scale WC particles with epitaxial growth layers are observed in the bottom of alloying layers. With the increase of Y2O3 content, the solidified microstructure with hypoeutectic morphology gradually refines, the number of the γ-(Fe, Ni) and M3C increases, and the number of martensite matrix decreases slightly. When Y2O3 content(mass fraction, the same below) is more than 1.0%, the solidified microstructure slightly coarsens. With the increase of Y2O3 content, the hardness of the alloying layers increases first and then decreases; the friction coefficient and the wear mass loss exhibit the opposite trend. When the Y2O3 content is 1.0%, the hardness of the alloying layer is the highest, which is 2.4 times of hardness of matrix; the friction coefficient and the wear mass loss are the lowest, which are 17% and 8.9% of the matrix respectively.

Keywords

• laser alloying
• wc/ni
• y₂o₃
• microstructure
• property