Turbula mixing characteristics of carbide powders and its influence on laser processing of stainless steel composite coatings

In this study, the mixing characteristics of feedstock carbides powders for laser synthesis of stainless steel composite coatings were investigated in a Turbula Shaker Mixer T2F. This research was aimed at determining the mixing parameters that give optimal powder homogeneity and determining any metallurgical interactions and/or bonding amongst powder during mixing. Blending/mixing of WC-9Co-4Cr, WC-10Ni and TiC powders mixture was performed in the mixer to prepare WC/TiC feedstock for laser melt injection. The constituent phases and microstructural characteristics of the as-received and feedstock powders were studied by Malvern particle size analyser, an X-ray diffractometer (XRD), a scanning electron microscope (SEM) equipped with an energy dispersive X-ray spectrometer (EDS). From the results obtained, it showed that the feedstock powder particles underwent diffusion and agglomeration. For a longer mixing time of 8 h, homogeneous distribution of the powder was obtained. However, it could be seen that diffusion, shear, segregation, random mixing and partial agglomeration of the powders were prominent. No new phases were formed. Also, the homogenized feedstock substantially improved the uniform distribution of the different carbides in the coatings as less dense powder particles were injected close to the bottom of the coated zone. Crown Copyright (C) 2012 Published by Elsevier BM. All rights reserved.