Effects of laser scanning strategies on selective laser melting of pure tungsten

Abstract

Three types of scanning strategies, including the chessboard scanning strategy, the zigzag scanning strategy and the remelting scanning strategy, were conducted to study the effects of scanning strategies on surface morphology, microstructure, mechanical properties and the grain orientation of selective laser melted pure tungsten. The results showed that the pores and cracks were main defects in SLM-processed tungsten parts. The pores could be eliminated using the remelting scanning strategy. However, the cracks seemed to be inevitable regardless of the applied scanning strategies. The microstructures of SLM-processed tungsten were columnar grains and showed strong epitaxial growth along the building direction. A compressive strength of 923 MPa with an elongation of 7.7% was obtained when the zigzag scanning strategy was applied, which was the highest among the three scanning strategies. By changing the scanning strategies, the texture of SLM-processed tungsten in the direction of processing could be changed.

Liquid vortexes and flows induced by femtosecond laser ablation in liquid governing formation of circular and crisscross LIPSS

“…Since the liquid vortex can exert an ultra-high pressure to the side walls of the formed structures, it may induce severe cracks to a brittle material such as tungsten (W). Previous reports have shown that metal W can be easily cracked upon the impact of laser pulses when the pressure exceeds its tensile stress limit 77,78 . To investigate whether the liquid vortexes can cause cracks to the microstructures, we checked the ablated W sample we have prepared for antireflective studies 51 .…”

Multiscale Hierarchical Micro/Nanostructures Created by Femtosecond Laser Ablation in Liquids for Polarization-Dependent Broadband Antireflection

“…As can be seen, both the thermal diffusivity and thermal conductivity of W are much higher than those of Ta, indicating that W should tend to cool more rapidly than Ta after laser heating. Additionally, the melting temperature of 3422 • C for W is relatively higher than that of 3017 • C for Ta [65,68]. For Ta, the smaller thermal conductivity and thermal diffusivity with a lower melting temperature must endow a relatively longer melting period than W so as to enable the interaction with surrounding oxygen species during fs-LAL.…”

Analytical Modelling of Temperature Distribution in SLM Process with Consideration of Scan Strategy Difference between Layers

“…They showed that with the same build, a long bidirectional scan strategy on one layer with 90-degree scan direction between layers led to least amount of residual stress. Guo et al [ 31 ] investigated the effect of scan strategy on surface quality, microstructure, and mechanical properties of the SLM build pure tungsten parts. They found that scan strategy significantly changed the surface morphology as well as the compressive stress.…”

“…However, there was not a model built to address the scan direction rotation between layers in SLM. Considering the importance of the rotation angle to the various aspects [ 28 , 29 , 30 , 31 , 32 ] of the build, it is important to include it into the analytical model. This paper proposes an analytical thermal model for SLM that considers the scan direction rotation between layers.…”