An investigation of hollow NiCrAl metal fiber porous material for high-temperature sealing

Porous metal fiber materials are a type of low-density material promising for functional and structural applications. Unlike traditional metal fiber porous materials, this study developed a novel hollow metal fiber porous material based on carbon fibers. Nickel was electroplated on the surface of the chopped carbon fiber, then the carbon core was removed by wet hydrogen sintering, and finally, Cr and Al were infiltrated by gas phase alloying to obtain the finished product. SEM showed that its internal structure was connected by metal fibers interlaced and overlapped to form a three-dimensional network porous structure. TEM and XRD proved that Ni (fcc) is the main phase of the material, and the addition of Cr and Al elements causes Ni lattice distortion. The compressive strength of the material at 900 °C is 4.44 MPa. In addition, the material's strength decreases with the heat treatment temperature increasing. The thermal conductivity of the NiCrAl porous material increases with the temperature, which is 0.143 W/(m·K) at room temperature and 0.416 W/(m·K) at 900 ℃. TG analyses showed that the NiCrAl porous material possessed excellent high-temperature and oxidation-resistance properties. Quartz lamp heating tests showed that the material had good thermal insulation, as the temperature dropped by about 230 °C after passing through the material. The average permeability of the material at room temperature is 5.46 e-6D. This metal fiber porous material has both the inherent properties of metal and the functional properties of porous materials such as lightweight, high-temperature resistance, heat insulation, etc. It is a promising high-temperature sealing material.