Abstract
Establishing processing routes for obtaining metal-matrix composites (MMCs) with uniformly-dispersed reinforcements is one of the main subjects in additively manufactured composite materials to achieve designed microstructures and mechanical properties. Here we report on the microstructural features of compositionally graded WC/Co-alloy composites additively manufactured by multi-beam laser directed energy deposition (multi-beam LDED). For tailoring microstructures of compositionally graded WC/Co-alloy composites with uniformly-dispersed reinforcements, the combinational method: the laser-beam defocus function in the multi-beam LDED system and granulated powder was attempted. By laser defocusing in the multi-beam LDED system, composites with uniformly-dispersed WC particles in Co alloy matrix was successfully obtained due to melting of Co bond in WC-12 wt.%Co granulated particles. It was found that the laser defocusing of multi-beam lasers affects temperature increase of flying powder during the laser focusing area, resulting in change of processing mode from melt-pool mode to thermal spray mode. The preferable property gradients in the WC/Co-alloy composites could be obtained by controlling the feeding rate of the powders and laser-beam defocus. These experimental results demonstrated the effectiveness of the laser-beam-defocus function in the multi-beam LDED system as a key factor for tailoring microstructures of additively-manufactured functionally graded MMCs with uniformly-dispersed reinforcements.
Highlights
Ceramic coatings applied to metallic components are intended to enhance the material properties such as heat, corrosion, and wear resistances[8]
Application of metal-matrix composites (MMCs) based functionally graded materials (FGMs)[9] for coatings is the most promising way to overcome this problem by smoothing the thermal stress distribution across the layers
There is no limitation for optimal particle size in terms of laser melting since ceramic particles are used for reinforcement
Summary
Ceramic coatings applied to metallic components are intended to enhance the material properties such as heat, corrosion, and wear resistances[8]. Establishing processing routes for obtaining MMCs with uniformly-dispersed reinforcements for a single-layer is one of the main subjects in the field of additively manufactured MMCs-based FGMs to achieve designed microstructures and mechanical properties. It should be difficult to obtain a deposited MMCs layer with uniformly dispersed small ceramic particles as shown in Fig. 2(c) due to the difference of mass density between ceramic and metallic particles. Our strategy for tailoring microstructures of MMCs with uniformly-dispersed reinforcements is based on the combinational method: the laser-beam defocus function in the multi-beam LDED system and granulated powder. Use of granulated powder provides a solution for these problems as a key factor to obtain finer microstructure of MMCs. In this study, AM process of compositionally graded MMCs on substrate by the multi-beam LDED system was investigated. Effects of laser-beam defocus Δf of the multi-beam LDED system on microstructural features of additively manufactured MMCs were focused on, to investigate the feasibility of this function as key factors for tailoring microstructure of MMCs with the use of granulated powder
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