研究目的
Exploring the feasibility of the manufacture, by L-PBF, of a WC-Co cutting tool material using a novel, and atypical, two-phase powder feedstock.
研究成果
For VED > 200 J/mm3, continuous tracks of WCM-12 wt.% Co can be formed; the tracks present minimal cracking and porosity but large WCM particles are found to be sintered to sides of the tracks. For VED < 200 J/mm3, as the energy is decreased, tracks become discontinuous with evidence of balling and powder bed denudation. A clear transition between conduction to keyhole-mode melting with respect to the values of volumetric energy density was observed and correlated to the melt-pool characteristics.
研究不足
The large particle size distribution imposed the necessity to use an unconventional layer thickness of 150 μm, which can affect the bulk density when a multi-layered component is to be fabricated. The low packing density of the feedstock produced significant shrinkage during melting.
1：Experimental Design and Method Selection
The study used a satelliting process to prepare a WCM-Co (12 wt.% Co) composite. Melting trials were undertaken to evaluate the consolidation behaviour of single tracks within a single layer.
2：Sample Selection and Data Sources
Commercially available powders, Spherotene? and Co, were used to prepare a composite feedstock. The composite feedstock was prepared with a nominal composition of WCM-Co (88–12) wt.% by using an innovative powder preparation method known as ‘satelliting’.
3：List of Experimental Equipment and Materials
A Realizer GmbH SLM-50, Germany, selective laser melting machine equipped with a continuous 100 W yttrium ?bre laser (YLM-100-AC) was used. The Spherotene? powder has a nominal size range of (45–125) μm and the Co metal powder (ABSCO Limited, Suffolk, UK) has a nominal particle size of (1–3) μm.
4：Experimental Procedures and Operational Workflow
The mixing process was divided into two steps: the dry mixing step, where the WCM and Co were mixed together with a certain weight ratio, and the wet step where poly-vinyl alcohol (PVA) binder was added. The resultant wet composite powder was then mixed by a gyroscopic mixer for 20 min to complete the mixing process. The resultant wet composite powder was then distributed onto a tray and put in an oven for 12 h to dry.
5：Data Analysis Methods
The morphological measurements of the single tracks produced were taken at the middle segments to investigate the melting and solidi?cation that occurs during the steady-state regime of laser. The width and height of these tracks was measured by an optical microscope (OM), Nikon Eclipse LV100ND.
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