An approach of laser remelting (LR) during laser melting deposition (LMD) process was applied to improve the forming quality and mechanical properties of the AlCoCuFeNi high entropy alloys (HEAs). In particular, the effect of laser remelting on the surface morphology, phase, microstructure and hardness of the parts were investigated using LSCM, SEM, XRD and Vickers microhardness tester. The results show that both LMD and LMD+LR samples dominantly consisted of a body-centered-cubic (BCC) and face-centered cubic (FCC) solid solution phases. There are many splash particles on the surface of the LMD part, which is attributed to the serious balling effect. The analysis shows that the LR process can improve the surface quality and microhardness of the LMD HEA samples due to the elimination of balling defects (microcracks and porosity).
Stainless steel has the characteristics of high temperature resistance, corrosion resistance, oxidation resistance and good welding performance. This work was studied the static ablation experiment of a new type of beam-coupled nanosecond laser to explore the changes of the main parameters of the laser, such as frequency and power, on the ablation aperture, hole depth, ablation area roughness and ablation morphology of stainless steel. The low-frequency 1 kHz and highfrequency 10 kHz were used to irradiate stainless steel to conduct a comparative analysis of the same frequency and different single pulse energy, and a comparative analysis of the same power and different frequencies. The influence of laser energy density and repetition frequency on the morphology of the processed microstructures was investigated. The ablation morphology of stainless steel becomes more severe with the increase of single pulse energy, and the ablation pore depth and pore size increase with the increase of single pulse energy.
In situ carbides (TiC/Cr7C3) reinforced CoCrMoNbTiC0.2 high-entropy alloy coatings were prepared on the Ti-6Al- 4V titanium alloy substrate by laser melting deposition technology. Effect of the laser power on the surface morphology, phase consistent, microstructure and microhardness were investigated. The results show that the coatings were composed of a simple BCC solid solution and a small amount of TiC and Cr7C3 carbides. The in-situ MC (TiC/Cr7C3) carbides were evenly distributed in the BCC matrix. The laser power has a significant impact on the forming quality and mechanical properties of the coatings. As the optimal laser power of 1500 W were applied, the coating mostly free of defects exhibited a fine dendritic microstructure. With the increasing laser power, the microhardness of the coatings was first increased and then decreased gradually. The highest microhardness of the coating (1500 W) was up to 650 HV0.5, which was 2 times higher than that of the substrate. The excellent mechanical properties of the coatings were attributed to the synergetic effects of the second phase strengthening, solid solution strengthening and fine microstructure.
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