Annular laser metal deposition (ALMD) is a rising technology that fabricates near-net-shaped components. In this research, a single factor experiment with 18 groups was designed to study the influence of process parameters on the geometric characteristics (bead width, bead height, fusion depth, and fusion line) and thermal history of Ti6Al4V tracks. The results show that discontinuous and uneven tracks with pores or large-sized incomplete fusion defects were observed when the laser power was less than 800 W or the defocus distance was −5 mm. The laser power had a positive effect on the bead width and height, while the scanning speed had the opposite effect. The shape of the fusion line varied at different defocus distances, and the straight fusion line could be obtained with the appropriate process parameters. The scanning speed was the parameter that had the greatest effect on the molten pool lifetime and solidification time as well as the cooling rate. In addition, the microstructure and microhardness of the thin wall sample were also studied. Many clusters with various sizes in different zones were distributed within the crystal. The microhardness ranged from 330 HV to 370 HV.

Laser metal deposition (LMD) is a technology for the production of near-net-shape components. It is necessary to control the manufacturing process to obtain good geometrical accuracy and metallurgical properties. In the present study, a closed-loop control method of melt pool temperature for the deposition of small Ti6Al4V blocks in open environment was proposed. Based on the developed melt pool temperature sensor and deposition height sensor, a closed-loop control system and proportional-integral (PI) controller were developed and tested. The results show that with a PI temperature controller, the melt pool temperature tends to the desired value and remains stable. Compared to the deposition block without the controller, a flatter surface and no oxidation phenomenon are obtained with the controller.

High-entropy alloys have been widely used in engineering manufacturing due to their hardness, good wear resistance, excellent corrosion resistance, and high-temperature oxidation resistance. However, it is inevitable that metallurgical defects, such as micro cracks and micro pores, are produced when preparing the coating, which affects the overall performance of the alloy to a certain extent. In view of this situation, cavitation water jet peening (CWJP) was used to strengthen the AlCoCrFeNi high-entropy alloy coating. The effect of CWJP impact time on the microstructure and mechanical properties of CWJP were investigated. The results show that CWJP can form an effective hardening layer on the surface layer of the AlCoCrFeNi high-entropy alloy. When the CWJP impact time was 4 h, the microhardness of the surface layer of the specimen was harder than that of 2 h and 6 h, and the CWJP impact time had little effect on the thickness of the hardening layer. Observing the surface of the untreated and CWJP-treated specimens using the EBSD test, it was evident that the microstructure was significantly homogenized, the grains were refined, and the proportion of small-angle grain boundaries increased. The system reveals the grain refinement mechanism of the AlCoCrFeNi high-entropy alloy coating during plastic deformation. This study aims to provide a new surface strengthening method for obtaining high-performance AlCoCrFeNi high-entropy alloy coatings.

Aiming its analysis at the poor hardness and wear-resistance of E690 high-strength steel, and the high hardness and good wear-resistance of AlCrN-coated, combined with the laser impact micro-modeling which can store oil lubrication, this paper carries out research on the synergistic wear reduction mechanism of laser impact micro-modeling AlCrN coated on the surface of E690 high-strength steel. Multi-arc ion plating technology is used to prepare the AlCrN coating on the laser-impact micro-modeling specimen; the micro-modeling AlCrN-coated specimen is subjected to a reciprocating friction test, and the hardness and residual stress of the coated surface are measured by equipment such as a residual stress meter and a microhardness tester. The microstructure and physical elements of the surface wear before and after the preparation of the coating are analyzed by scanning electron microscope (SEM), confocal three-dimensional morphometer and XRD diffractometer, respectively. The results show that the prepared AlCrN-coated materials were well-bonded to the substrate. Compared with the micro-molding-only specimens, the average friction coefficient and wear amount of the micro-molded AlCrN-coated specimens with different micro-molding densities and depths decreased compared with the micro-molded specimens; among them, the average friction coefficient of the specimens with a micro-molding density of 19.6% and a depth of 7.82 µm was 0.0936, which was the lowest. Additionally, the AlCrN coating enhances the stability of the friction process of the specimen and reduces the amount of wear of the specimen. Under the premise of ensuring the anti-wear and stability properties of the material, the best integrated friction performance was achieved at a micro-molding density of 19.6% and a depth of 24.72 µm. A synergistic wear reduction and lubrication model of micro-molding and AlCrN-coating was established.