A laser additive and subtractive hybrid manufacturing technology was proposed to repair Inconel 718 cracks in this paper. Microstructures and the mechanical properties such as the micro-hardness, the tensile strength, and the friction-wear of the repair zone were investigated in detail. The microstructure analysis showed that a metallurgical bonding could be achieved between the repair zone and the matrix. The typically columnar and dendrite crystal appeared in the repaired zone, and the crystal epitaxial grew along the deposition direction, and the heat-affected zone in the groove boundary was coarse equiaxial crystal. The mechanical test result showed that the micro-hardness and tensile strength of the repaired tissue was about 87% and 89% of the original Inconel 718 wrought substrate. And, the wear resistance of the repaired zone was similar to that of the substrate. It was found that the surface quality of the repair zone for laser polishing is better than that for mechanical milling.

Refractory high-entropy alloys (RHEAs) exhibit outstanding softening resistance and thermal stability at elevated temperatures. Unfortunately, poor ductility at room temperature has remained the critical issue for their processability and practical application. In this study, an original-type fabrication method of RHEA was proposed, using multi-walled carbon nanotubes (MWCNTs) to enhance the alloy prepared via laser melting deposition (LMD) technology. The processing optimization, microstructure evolution and mechanical properties were systematically investigated for LMD processing of CNTs/CoCrMoNbTi_0.4 RHEA. The results have shown that CNTs/CoCrMoNbTi_0.4 RHEA have a polycrystalline structure (BCC, HCP, and TiC). As the optimal LMD-processing parameters of laser linear energy density of 3.6 J/mm were applied, owing to the formation of high densification and an ultrafine microstructure, the fully dense LMD-processed alloy exhibited high microhardness of 1015 HV_0.5, fracture strength of 2110.5 MPa, and fracture strain of 2.39%. The solid solution strengthening and load transfer are considered as the main strengthening mechanisms occurring simultaneously during compressive tests at room temperature, leading to excellent mechanical properties of LMD-processed CNTs/CoCrMoNbTi_0.4 RHEA, which explores the potential application of RHEAs.

This study employed different spot pattern lasers to clean the oxide film on the surface of a TC4 titanium alloy. The variation in temperature field and ablation depth during the laser cleaning process was simulated by establishing a finite element model. The effects of various laser processing parameters on the micromorphology, elemental composition, and surface roughness of the TC4 titanium alloy were analyzed. The results show that as the laser energy density increases, both the temperature field and ablation depth increase as well. Under optimal laser processing parameters, the laser energy density is 5.27 J/cm², with a repetition frequency of 300 kHz and a scanning speed of 6000 mm/s. A comparison of the cleaning effects of Gaussian pulse lasers and Flat-top pulse lasers reveals that the Gaussian pulse laser causes less damage to the TC4 titanium alloy, resulting in lower oxygen content and roughness values after cleaning compared to Flat-top pulse laser cleaning.