A feasibility study on advanced methodology to produce high-performance nano WC-Co granule feedstock for thermal spraying

Abstract

A feasibility study was conducted, in order to fabricate WC-Co powder granule as high-performance feedstock for thermal spraying process, by spray drying weakly flocculated nano-particulate slurries under various conditions. The defects were evaluated with respect to the amount of additives to prepare spherical WC-Co feedstock powders with few morphological defects and homogeneous microstructures. The characteristics of feedstock powders heat-treated at 850-1200 degrees C were analyzed using SEM, EPMA, and Hg-porosimetry. The microstructure investigation revealed that the relative portion of larger pores around 10 mu m increased with increasing heat-treatment temperature. On the other hand, the relative portion. of smaller pores of I mu m decreased due to the coalescence of WC particles, leading to dense feedstock powders with less defects such as hollow or craters. The hardness of thermal-sprayed coat developed with the feedstock in this study, which had exceptionally high feedstock strength, was superior to that of any other sprayed coat obtained with commercial feedstock powders.