Paper PS-TuP25
Plasma Surface Texturing of Metals

Tuesday, October 21, 2008, 6:30 pm, Room Hall D

A novel plasma process for creating a nanometer and micron-scale textures on MP35N alloy surfaces using radio-frequency (RF) inert gas plasmas was investigated, with a focus on characterizing the relationship between process variables and the resulting microstructure. This unique plasma texturing technology provides several advantages over other coating-based texturing processes. Because it is a surface modification process, coating delamination and loose particulates, which would cause serious problems in biomedical applications, are not of concern. Possible applications of the textured surfaces include drug reservoirs, surfaces that promote tissue or bone in-growth, and any applications benefited by high surface areas. In the plasma texturing process, metal samples were placed directly on the substrate holder that was electrically connected to an RF electrode. Typical process parameters for Ar plasma texturing included 200W to 800W of power, pressures of 20 mTorr to 80 mTorr, and process times of 8 min to 10 min. A variety of surface textures with differently sized features have been formed varying from individual pillars to three dimensional, interconnected porous structures. The microstructures that evolve were believed to result from the loss of material from the metal sample, due to the combination of interactions of Ar ions with the sample and subsequent heating of the metal surfaces. The amount of material removed from MP35N alloy samples during texturing ranged from 4 to 10 % of the initial mass of the sample depending on the degree of texturing. Process variables, including RF energy and pressure, as well as properties of the material to be textured (thermal and electrical transport properties and sample geometry) were all found to affect the degree of texturing and type of microstructure formed. To create surfaces with more complex textures, the plasma textured surface has been modified by subsequent surface treatments and depositions. This secondary process can form additional microstructures on the already textured surface or modify surface chemistry and properties.