Effect of annealing treatment on the structure and properties of the nanograined Ni-Al coatings produced by mechanical alloying coating process

An mechanical alloying coating (MA) process was used for the deposition of the nanograined Ni-Al coatings. During the MA process, the substrate surface was subjected to high-energy ball impacts. The repeated substrate-to-ball collisions made the coated Ni-Al particles cold weld to each other and to the substrate. The MA method allows nanograined Ni-Al coatings to be produced on different substrates in a short time at room temperature in an ambient atmosphere. Under the applied compressive loading, the substrate became strongly deformed. The grain refinement occurred and many randomly orientated nanosized grains developed near the substrate surface. Annealing treatment in temperatures ranging between 400 ◦C and 600 ◦C improved Ni-Al compound of the coatings and increased hardness. The nanoparticles had a tendency to consolidate with increasing annealing temperature. The growth of crystallites started at 400 ◦C. After annealing at 600 ◦C, a solid state reaction between Al and Ni leads to the formation of a new phase that could be intermetallic compound Ni-Al.

Keywords:

Coating , heat treatment , Intermetallics , Nanostructured material