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 cer amic 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 comp osites. First, a hot isostatic pressing (HIP) technique was used to produce bulk Ni-Al2O3 alloys. These composite samples contained 0-45 vol.% of Al2O 3 with an average particle size of 12 mu m. Second, an electrodeposition te chnique was developed and Ni-Al2O3, coatings with various volume fractionso f Al2O3 (0-39 vol%) were produced on a pure Ni substrate. In contrast to th e bulk powder composites, the electrodeposited composites contained much sm aller Al2O3 particles (approximate to 1 mu m) Erosion testing was conducted at impact angle of 90 degrees using angular alumina. It was found that for both type of composites. an increase in Al2O3 content led to an increase i n erosion rate of the composites and pure Ni showed the best erosion resist ance. However, the electrodeposited Ni-Al2O3 alloys exhibited better erosio n resistance than the powder processed Ni-Al2O3 alloys. For erosion test co nditions used, the smaller Al2O3 particles in the Ni matrix were more benef icial in terms of erosion resistance than the large Al2O3 particles. (C) 20 00 Elsevier Science S.A. All rights reserved.