Objective GH3536 is a typical nickel-based solid solution strengthened high-temperature alloy with good oxidation resistance, corrosion resistance, as well as cold and hot processing formability and weldability, which is suitable for manufacturing aero-engine combustion chambers and other high-temperature components. The failure mode of the combustion chamber is mainly mechanical damage and shell cracks. Laser-cladding technology can be used to repair the failures, which can effectively reduce the combustion chamber test's cost. However, the topography of the area to be repaired is mainly curved or inclined surface, and the operation space is limited. Therefore, it is necessary to study the repair process and role of laser-cladding technology on the inclined substrate. In this study, we analyzed the influence of factors such as inclination angle and gravity on the temperature field, flow field, and final contour of the molten pool during GH3536 cladding on the inclined surface with both experimental and simulation methods and laid a foundation for the application of laser-cladding technology to repair inclined substrates, such as combustion chambers.

Methods This study investigated the process and role of GH3536 laser cladding on inclined surfaces with both experimental and simulation methods. First, we used the orthogonal experiment to analyze the influence of factors such as laser power and powder-feeding flow rate on the melting height and profile during GH3536 laser cladding on a plane substrate. Then, we performed a controlled variable experiment of laser cladding on an inclined surface to analyze the influence of factors such as the inclination of the substrate, laser power, and powder-feeding flow rate on the melting height. Afterward, we established a computational-fluid-dynamics model to simulate GH3536 laser cladding on inclined surfaces and compared the cladding profile and penetration depth via simulation and experiment to verify the effectiveness of the model. Finally, we investigated the influence of the inclination angle of the inclined surface on the front contour, internal temperature field, and the flow field of the cladding layer.

Results and Discussions In the orthogonal experiment, within a set range of the experimental parameters, when the laser power is selected as the lowest value of 1000 W, and the powder mass flow rate is selected as the maximum value of 18 g/min, the melting height is the largest (Fig.4). When the substrate starts to tilt, the melting height gradually decreases with the increase in the inclination angle. A moderate increase in the laser power and powder feed mass flow can compensate for the decrease in the melting height. Further, at the same inclination angle, the melting height increases during upward cladding (Fig.8). In the simulation model, comparing the quasi-steady state molten pool contours under different substrate inclination angles, the slope angle of the molten pool front contour decreases with the increase in the inclination angle, and the front slope angle during upward cladding is slightly smaller than that of downward cladding (Fig.10). In addition, comparing the internal flow field of the molten pool under different substrate inclination angles, the front and rear flow fields appeared in the quasi-steady molten pool, and the latter is stronger. They are separated by the high-temperature zone of the molten pool. The substrate inclination has a significant influence on the flow field in the molten pool. During upward cladding, gravity strengthens the rear flow field and weakens the front flow field, thereby accelerating their divergence. At their divergent positions, the contour of the molten pool also shows obvious slope angle changes (Fig.12). The changes in both flow fields correspond to the changes in the front of the upper molten pool and the changes in the melt height. It can be inferred that the flow fields have a significant influence on the profile of the molten pool—the front flow field dominates the front slope angle of the molten pool, while the rear flow field dominates the molten pool height.

Conclusions The tilt of the substrate decreases the laser energy and powder concentration at the cladding area, thereby reducing the cladding height considerably. A moderate increase in the laser power and powder delivery mass flow rate can compensate for the decrease. The Marangoni convection in the molten pool is divided into two flow fields—the front and rear flow fields. The latter dominates the height of the cladding layer, while the former dominates the slope angle of the cladding layer. The difference in gravity influence due to the inclination of the substrate has a significant influence on the contour of the molten pool, especially the front contour. In addition, the difference in the cladding direction will significantly change the effect of gravity on the internal flow field, resulting in a completely different front contour and front slope angle: when the inclination angle is positive, the gravity component promotes the rear flow field, accelerates the divergence of both flow fields, leading to the concave phenomenon of the molten pool, and reduces the front slope angle and has higher melting height compared with a negative inclination angle.