Consolidation of surface coatings by friction stir techniques

Abstract

Friction Stir Processing (FSP) is an emerging technology that allows for the processing of regions near the surface of a material in order to improve upon the existing mechanical properties. Aluminum alloy samples were plasma sprayed with a Titanium-Nickel-Chrome coating or a Titanium coating. Single and multiple pass experiments were performed with both a pinned and a pinless FSP tool at rotation speeds of 400, 800 and 1500 revolutions per minute; all traverses were done at four inches per minute. Optical and electron microscopy methods were then used to determine the success at consolidating the relatively hard and porous Titanium based coatings onto the Aluminum alloy surface. Results showed that the most successful results were accomplished using a flat, pinless tool, with minimal downward force applied to the sample. The Titanium coatings were visibly less porous at microscopic levels, and there was also considerably less separation at the coating-base interface. Energy dispersive x-ray spectroscopy showed very little mixing of the base material and the plasma sprayed coating.