Defect Control Process and Mechanism of Laser Additive Manufacturing of Cemented Carbides
Selective laser melting(SLM)technology is currently one of the primary processes for additive manufacturing of WC-Co cemented carbides.However,due to the significant differences in physical properties between the metallic and ceramic phases,obtaining crack-free and pore-free cemented carbide components with high performance through SLM printing remains a significant challenge.This work first investigated the influence of laser power,scanning speed,and hatch spacing on the porosity of the fabricated specimens by using WC-Ti powder,which has a relatively small difference in melting points.On this basis,a function relationship between laser process parameters and the density of the printed parts was established.It was found that the scanning speed had the most significant impact on the density of the fabricated specimens.Moreover,by further synergistically optimizing the laser spot size and powder particle size,the porosity of SLM-printed WC-Co cemented carbides was reduced to 1.5%,and cracks were eliminated.Molecular dynamics simulations were employed to reveal the mechanism by which the optimized matching of laser spot size and powder particle size inhibited the formation of cracks,pores,and other defects in the printed cemented carbides.Based on optimized WC-Co composite powder,SLM technology,and subsequent heat treatment conditions,a nearly fully dense cemented carbide cutting insert with a bimodal grain microstructure was fabricated.The insert exhibited a Vickers hardness of(1 300±20)HV30,a bending strength of(1 020±130)MPa,and a compressive strength of(3 520±240)MPa.The overall mechanical properties of this material are comparable to those of sintered cemented carbides with similar compositions and grain sizes,demonstrating promising application prospects.
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