Effect of molybdenum concentration on mechanical, microstructural, corrosion, and tribological properties of (Al3Ni–Al3Ni2)100-x -Mox (x= 3, 5, and 7 wt%) composites

Abstract

The nickel aluminide intermetallic is a crucial material for structural components in high-temperature applications. This study investigates the impact of adding Mo at three different concentrations (3, 5, and 7 wt%) to the Al3Ni–Al3Ni2 intermetallic powder produced by mechanical alloying. The composite powders are then consolidated by cold compaction and sintered at a temperature of 800 °C. The resulting Al3Ni–Al3Ni2 intermetallic, Al3Ni–Al3Ni2–Mo3, Al3Ni–Al3Ni2–Mo5, and Al3Ni–Al3Ni2–Mo7 composites are examined for their mechanical, metallurgical, corrosion, and tribological behaviors. The microstructure showed that adding 3 and 5 wt% of Mo to the Al3Ni–Al3Ni2 intermetallic resulted in good metallurgical bonding, less porosity, and grain refinement with a homogeneous distribution. However, the addition of 7 wt% Mo resulted in high porosity with an inhomogeneous distribution. The Al3Ni–Al3Ni2–Mo5 composite showed the highest yield strength (947 MPa), ultimate tensile strength (1365 MPa), and hardness (420.4 HV) due to the dispersion-strengthening effect and grain refinement. On the other hand, the Al3Ni–Al3Ni2–Mo7 composite exhibited lower values than the Al3Ni–Al3Ni2–Mo3 and Al3Ni–Al3Ni2–Mo5 composites due to the inhomogeneous distribution of the Mo elements observed through energy dispersive X-ray spectroscopy (EDS) mapping. The presence of a passive film on the surface of the Al3Ni–Al3Ni2–Mo5 composite resulted in higher corrosion resistance and lower corrosion rate (0.0221 mm/yr) compared to other samples. The wear test results showed that the Al3Ni–Al3Ni2–Mo5 composite exhibits better wear resistance than the other samples due to tribo oxide layers.