Effect of molybdenum concentration on mechanical, microstructural, corrosion, and tribological properties of (Al 3 Ni-Al 3 Ni 2 ) 100-x-Mo x (x=3, 5, and 7 wt%) composites

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 Al 3 Ni-Al 3 Ni 2 intermetallic powder produced by mechanical alloying. The composite powders are then consolidated by cold compaction and sintered at a temperature of 800 degrees C. The resulting Al 3 Ni-Al 3 Ni 2 intermetallic, Al 3 Ni-Al 3 Ni 2 - Mo 3 , Al 3 Ni-Al 3 Ni 2 - Mo 5 , and Al 3 Ni-Al 3 Ni 2 - Mo 7 composites are examined for their mechanical, metallurgical, corrosion, and tribological behaviors. The microstructure showed that adding 3 and 5 wt% of Mo to the Al 3 Ni-Al 3 Ni 2 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 Al 3 Ni-Al 3 Ni 2 - Mo 5 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 Al 3 Ni-Al 3 Ni 2 - Mo 7 composite exhibited lower values than the Al 3 Ni- -Al 3 Ni 2 - Mo 3 and Al 3 Ni-Al 3 Ni 2 - Mo 5 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 Al 3 Ni-Al 3 Ni 2 - Mo 5 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 Al 3 Ni-Al 3 Ni 2 - Mo 5 composite exhibits better wear resistance than the other samples due to tribo oxide layers.