Surface modification of lotus-type porous copper by aluminization

This paper explores the feasibility to aluminize lotus-type porous copper to prolong the service life of lotus-type porous copper in applications. To achieve this goal, smaller particles of α-Al2O3, Al and NH4Cl were employed for aluminization process considering the difficulty arising from shielding effect by pore walls. The structure of the aluminized coating including thickness, elements profile and phase composition was characterized. It is found that the deposition of aluminized coating on pore walls of the lotus-type porous copper is feasible. It is indicated that the pore size has to be more than 300 µm in order to obtain a decent aluminized coating on pore walls of the lotus-type porous copper under the present experimental conditions. The coating is consisted of an alloy layer (first α-Cu, then a mixture of Cu3Al and Cu9Al4) and a re-solidified layer (α-Al2O3 particles incorporated in Al substrate). Furthermore, Vickers hardness, sliding property and wear resistance were evaluated. The hardness is enhanced by a factor of three, which is distributed from 105 to 302 HV0.01 from copper substrate to the coating surface. It is also proved that the aluminized coating can significantly reduce the wear rate of the lotus-type porous copper by shifting the wear mechanism from adhesive mode to plowing mode by the improved hardness.