Composite copper/stainless steel coated powders

摘要

The present research work concerns the development of new composites based on austenitic stainless steel (SS) or copper (Cu) microsized powders coated with thin nanostructured layers of copper or stainless steels, respectively. A home-manufactured magnetron sputtering system equipped with a powder vibration device was used to coat the powders. A detailed analysis of the coated copper or stainless steel powders shows a uniform nanocrystalline layer whatever the shape of the particles. The powders' coating process associates high efficiency for coating micro- and submicrometric powders, with a submicrometric or a nanometric layer having a similar chemical composition to the targets previously selected. A significant decrease of the crystallite size and an increase of high surface/volume ratio, are suitable to improve their friction coefficient, wettability and sinterability. The thermal evolution of the coated powders was studied using a hot chamber coupled to XRD and DTA-TG apparatus. The coated copper powders show above 700 ℃ the formation of a typical intermetallic phase Cu_4Ni, that occurs in bcc stainless steel, where copper is an alloy element, and no vestiges of the coating is detected after heat treatment. The stainless steel coated powders reveal the formation of Fe_4Cu_3 at temperatures higher than 900 ℃.