Microstructural and Mechanical Properties of WC-17Co Deposited Using Laser Direct Energy Deposition (LDED) and High-Velocity Oxygen Fuel (HVOF)

Abstract

Recently, laser deposition technologies have made significant advancements in their ability to manufacture high-temperature metals and ceramics. One of these technologies, known as laser direct energy deposition (LDED), has the potential to deposit a wide range of materials from polymers to refractory materials, ceramics and functionally graded materials. This study evaluates major microstructural characteristics of WC-17 Co additively manufactured by LDED technology. A LDED-manufactured WC-Co sample was examined by optical microscopy (OM), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and x-ray diffraction (XRD). Electron backscatter diffraction (EBSD) experiment was also performed to validate results obtained from XRD test. This material is commonly used for deposition of protective coatings due to its high hardness and excellent wear resistance. To this end, hardness and wear resistance of the LDED-processed samples were also investigated in this study. All the tests were also repeated on high-velocity oxygen fuel (HVOF)-deposited WC-Co with the same composition for the purpose of comparison. LDED sample showed slightly higher porosity (~4%) compared to the HVOF one (~3%). Both samples experience decomposition of the carbides into compound phases as indicated by XRD results. EBSD test results also confirmed the ones obtained from XRD and detected WC, Co, W₂C, and W₃Co₃C in both samples while some more complex phases such as W₉Co₃C₄ was found in LDED sample. The LDED-deposited sample also displays unique dendritic and eutectic structures that improve the hardness and wear properties compared to the homogenous HVOF coating instead of higher porosity level. The higher wear resistance of LDED sample is also associated with its higher hardness.