Repairing processing is a significant method for damaged high-cost Ti-6Al-4V components to decrease economic loss, which usually utilizes a welding technique. For a large-size structural component, welding processing is commonly completed in air conditioning, which makes it difficult to avoid welding defects. To this end, an appropriate matching technique is important for improving welding performance. In the present research, asynchronized laser shock peening (ALSP) and synchronized laser shock peening (SLSP) techniques were utilized to decrease the influence of macro welding defects on laser-welded Ti-6Al-4V joints. The results show that SLSP has a greater effect on inducing surface plastic deformation on Ti-6Al-4V joints with a pitting depth of more than 25 microns while ALSP can lead to a pitting depth of about 15 microns. Through micro-CT observation a long hot crack exists in the central area of as-welded joints with a length of about 2.24 mm, accompanied by lots of pores in different sizes on double sides. After ALSP processing, some pores are eliminated while others are enlarged, and one-side crack tips present closure morphology. However, some microcracks exist on the side-wall of hot cracks. With the influence of SLSP, significant shrinkage of pores can be observed and both sides of crack tips tend to be closed, which presents a better effect than ALSP processing. Moreover, greater effects of grain refinement and thermal stress release could be achieved by SLSP processing than ALSP, which can be ascribed to dynamic recrystallization. For the as-welded joint, the ultimate tensile strength (UTS) and elongation (EL) values are 418 MPa and 0.73%, respectively. The values of UTS and EL in the ALSP processed joint are increased to 437 MPa and 1.07%, which are 4.55% and 46.48% higher than the as-welded joint, respectively. Such values after SLSP processing are 498 MPa and 1.23%, which are 19.14% and 68.49% higher than the as-welded joint, respectively.

Conventional laser processing of metals will form serious heat affected zone, micro cracks, burrs and recast layer, resulting in rough machined surface and serious slag accumulation. As a new type of laser-waterjet composite processing method, waterjet guided laser can reduce or even eliminate heat affected zone, thermal crack, recast layer and burr. It has the advantages of high surface quality, strong depth ability and large depth-to-diameter ratio structure. Nickel-based single crystal superalloy is widely used in advanced aero-engine turbine blades for their excellent overall performance. With waterjet guided laser processing technology, this paper study the influence of process parameters on the grooving morphology and quality of DD6 nickel-based single crystal superalloy. A multi-factor study on the influence of laser power, laser repetition frequency, waterjet velocity and feeding speed on grooving was carried out with a self-developed waterjet guided laser processing device. The depth-to-width ratio and sidewall taper of the machined groove were measured and analyzed by using a three-dimensional confocal laser scanning microscope. The experimental results show that the grooves taper can be decreased with reducing the laser repetition frequency and increasing the laser power. The grooves large depth processing is improved by reducing the feeding speed, increasing the laser power, reducing the laser repetition frequency and increasing the waterjet velocity. The cutting experiment of 1 mm DD6 nickel-based single crystal superalloy was achieved with better processing process parameters, and it was found that the upper and lower surface roughness of the cutting surface was inconsistent, providing a theoretical basis for the study of high quality processing of nickel-based single-crystal superalloy by waterjet guided laser.

Water jet-guided laser technology is an efficient processing technology that offers the advantages of a small heataffected zone and strong depth capability when processing a variety of difficult-to-process materials. However, the surface of the laminar water column can form irregular disturbances due to nozzle damage and other factors, ultimately leading to an uneven distribution of laser light intensity, causing a loss of laser power. In this paper, the relationship between the quality, morphology and coupling alignment errors of the water column on the optical transmission efficiency of water-guided lasers is investigated in depth with ray tracing method. Besides, the water column surface variable-angle prismatic disturbance model is established, considering the characteristics of the real water column to research the impact of the real situation relationship. The results show that the loss of laser energy is more severe as the complexity of the surface morphology of the water column increases. In addition, laser coupling alignment errors are studied. The results show that a circular distribution is formed in the water column when the alignment deviation occurs. Finally, the reasons affecting the laminar flow conditions are analyzed to provide theoretical support for efficient laminar coupled light transmission.