Effect of Cobalt-Based Filler Wire Composition on the Microstructure and High-Temperature Properties of Cladding...

To improve the high-temperature service performance of cladding layers on DD5 single crystal superalloy, this study comparatively investigated the effects of two cobalt-based filler wires, PMet931 and PMet994, on the microstructural evolution, hardness, high-temperature tensile properties, and friction and wear behavior of the cladding layers. The results show that PMet931, with a higher Ni content, exhibits better compositional compatibility and interfacial metallurgical compatibility with the DD5 Ni-based substrate. In contrast, the higher W, C, and Cr contents in PMet994 promote the formation of W/Cr-rich secondary phases and grain refinement, resulting in higher hardness and better high-temperature strength retention. Both filler wires can form continuous cladding layers on the DD5 surface. The PMet931 cladding layer shows a more homogeneous microstructure and a smoother interfacial transition, whereas the PMet994 cladding layer contains more secondary phases and exhibits more pronounced strengthening features. Mechanical testing indicates that PMet931 provides a better strength ductility balance at room temperature, while PMet994 shows higher strength and hardness retention over the range of 800-1050 °C, with a tensile strength at 1050 °C approximately 53% higher than that of PMet931. The friction and wear results show that the wear rate of the PMet994 cladding layer was significantly lower than that of the PMet931 cladding layer at 800 °C, whereas the difference between the two cladding layers decreased at higher temperatures. This study demonstrates that filler wire composition significantly affects the high-temperature performance of DD5 cladding layers by regulating secondary phase precipitation, interfacial compatibility, and microstructural stability.