Wet erosion damage of Cr 3 C 2 /Al 2 O 3 composite
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This study focused on investigating the role of interfacial microcracking of injection-molded Cr3C2/Al2O3 composite on the erosion mechanism under an impingement erosion test rig. The surface residual strain (stresses) as well as damage were compared in both airborne and wet erosion. The delays in crack propagation at interfacial or triple points and the crack direction changes were frequently observed in the composite. Spontaneous microcracking induced from sintering process, due to thermal expansion mismatch between alumina and chromium carbide, played a key role in erosion mechanism.
I. INTRODUCTION
Ceramic matrix composites have attracted much attention for advanced structural and tribological applications over the past several decades. Like many ceramic materials, chromium carbide can be used as wear-resistant liner for industrial applications where solid particles and slurry are transported.1–3 Erosion by solid entrained on gas or liquid streams can cause severe damage in systems such as gas turbines, cyclone generators, fluidized beds, and boilers.4–6 Wet erosive wear behavior of brittle solids by solid particles is rather complicated. It could depend on the microstructure and property of both target materials and erodent particles and their interactions involving velocity and impingement angles. It was previously reported that the erosive wear rate of hot-pressed Cr3C2/Al2O3 composite decreased linearly by increasing Cr3C2 content and was lowered by a factor of two to three, compared to that in pure alumina.1 Recently, wet erosive wear of alumina densified with magnesium silicate additions and liquid-sintered alumina were reported.7,8 They proposed grain boundary compressive hoop stresses, caused by the thermal expansion mismatch between a continuous magnesium silicate film and alumina grains, could improve wet erosion resistance. Grain size effects have been found important in both abrasive and erosive wear, with low wear rates associated with fine grain size.9–12 Two wear mechanisms, microfracture and grain detachment, and tribochemical wear are identified during the wet erosive wear of pure polycrystalline alumina.12 Although considerable efforts have been devoted to enhancing the wear resistance, little has been reported concerning the wet erosion damage. a)
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http://journals.cambridge.org
J. Mater. Res., Vol. 18, No. 5, May 2003 Downloaded: 19 Mar 2015
This study focused on investigating the role of interfacial microcrackings on the erosion mechanism, and the surface residual strain (stresses) and damage due to wet erosion. The Cr3C2/Al2O3 composite samples were prepared by injection molding and pressureless sintering. The injection molding technique was used to produce complex-shaped components of high-dimensional accuracy, which have potential for automated production. II. EXPERIMENTAL A. Material preparation
Alumina powders (A16-SG, Alcoa Industrial Chemicals, PA, 0.5 m) were mixed with Cr3C2 (2 m, grade 160, H.C
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