EROSION MECHANISM IN DUCTILE METALS

Abstract The removal of material from the surface of a ductile metal by small impacting particles is a design consideration to the builders of synthetic fuels plants that utilize pulverized coal to produce gaseous forms of fuel. A series of room temperature experiments was conducted to determine the mechanism of material removal when an erosive particle stream impacted on a ductile metal surface. Al 1100-0 metal and Al 7075-T6 alloy were used for the target and 600 μm SiC particles moving at a velocity of 100 ft s−1 in air were used for the eroding stream. It was found that a combined forgingextrusion mechanism which produces small highly distressed platelets of target material that are knocked off the surface by succeeding particle impacts is responsible for erosion at both low and high impingement angles. The large strains that produce the platelets occur in a thin surface region which is heated near to or to the annealing temperature of the metal as a result of adiabatic shear deformation. Beneath the soft surface layer there is a region that has been cold worked by impact-particle-induced plastic deformation. This hard subsurface layer, once formed, increases the efficiency of platelet formation at the surface and the erosion rate increases to a constant level. This proposed mechanism is a significant departure from the previously accepted micromachining mechanism of ductile metal erosion.