Research on Preparation Process of Ultrafine Spherical WC-10Co-4Cr Spraying Powder Based on Spray Granulation

HVAF WC-10Co-4Cr coating has been applied to the extreme wear protection of lightweight titanium alloy workpieces. However, the new generation of lightweight titanium alloy inner bore wear-resistant workpieces is faced with strong wear and instantaneous high-temperature airflow erosion during service, which requires a WC-10Co-4Cr wear-resistant coating with low surface roughness, high thickness and high toughness. In addition, its small diameter inner hole also requires the rapid heating, melting and acceleration performance of sprayed powder during spraying. At present, the finest spraying powder used in this system is generally in the range of 5–15 μm, which faces difficulties in meeting the above requirements. In order to solve this problem, the preparation of 2–10 μm spherical spray powder was studied though a spray granulation experiment, and the change law of powder morphology with the solid content of pre-spray slurry was explored. The suitable binder was selected through a slurry sedimentation test and viscosity test, so that the gunable solid content of the pre-sprayed slurry was reduced from 60 wt.% to 12.5% by weight, which significantly reduces the particle size of the powder obtained by spray granulation. When the solid content of pre-sprayed slurry is 12.5 wt.%, sodium carboxymethyl cellulose (CMC-Na) is selected as the binder, and the binder content is 2 wt.%, the particle size range of powder obtained by spray granulation process reaches 2–10 μm, and the median particle size reaches 5 μm. After heat treatment, the powder is spherical and dense inside. The research results provide technical support for preparing high-performance ultrafine WC-10Cr-4Co spherical powder with wear-resistant coating for light titanium alloy.