Synthesis and characterization of nanocrystalline Al2O3-Ni(Cr) particles using high-energy mechanical alloying process

Structural materials in many technology intensive high end applications such as petrochemical, industrial manufacturing, aerospace, automotive, and bio-resources have to operate under extreme conditions of temperature, pressure and slurry erosion/abrasion. One way to protect these surfaces is the use of novel material solutions on industry-standard substrates limited in mechanical strength and wear life under high temperature oxidation erosion and other corrosive degradation environments. This paper presents experimental research results pertinent to first attempt to synthesize nanocrystalline Al2O3-Ni(Cr) cermet composite particles using high-energy mechanical alloying (HE-MA) technique in a cryogenically-controlled atmosphere. A detailed design of experiment (DoE) was carried out to process the precursor materials. Results from SEM and XRD analyses reveal the progressive formation of nanocrystalline Al2O3 grains embedded in the micron-sized Ni(Cr) alloy particles. It is shown that milling time and precursor particle structure play a key role in obtaining the desired microstructure and particle size distribution in the processed feedstock. Further, particles with homogeneous distribution of Al2O3 grains can be produced at a milling speed of 150 rpm following a 24-hour run.