The effect of second phase volume fraction on the erosion resistance of metal-matrix composites

Metal-matrix composites that consist of a ductile metal-matrix and hard ceramic particles are often used as materials of choice for protection against solid particle erosion. In this study, a model Ni–Al2O3 system was chosen to analyze the effect of hard second phase particles on erosion resistance. This system consists of hard Al2O3 particles dispersed within a ductile Ni matrix. Two processing techniques were used to fabricate the Ni–Al2O3 composites. First, a hot isostatic pressing (HIP) technique was used to produce bulk Ni–Al2O3 alloys. These composite samples contained 0–45 vol.% of Al2O3 with an average particle size of 12 μm. Second, an electrodeposition technique was developed and Ni–Al2O3 coatings with various volume fractions of Al2O3 (0–39 vol.%) were produced on a pure Ni substrate. In contrast to the bulk powder composites, the electrodeposited composites contained much smaller Al2O3 particles (≈1 μm). Erosion testing was conducted at impact angle of 90° using angular alumina. It was found that for both type of composites, an increase in Al2O3 content led to an increase in erosion rate of the composites and pure Ni showed the best erosion resistance. However, the electrodeposited Ni–Al2O3 alloys exhibited better erosion resistance than the powder processed Ni–Al2O3 alloys. For erosion test conditions used, the smaller Al2O3 particles in the Ni matrix were more beneficial in terms of erosion resistance than the large Al2O3 particles.