Surface oxides on metal powders: An overview of the effect of alloy composition and manufacturing method

The quality and usefulness of powder are strongly determined by the surface composition of the powder. Amount of oxides, their composition and spatial distribution on the powder surface and within a particle determine the requirements for the subsequent consolidation process. This paper summarizes possibilities of qualitative and quantitative analysis of powder surface chemistry by a variety of methods, starting from surface-sensitive chemical analyses by XPS, AES, HR SEM coupled with EDX and FIB, and modern thermoanalytical techniques. Effect of the different powder manufacturing methods (water and gas atomisation, EIGA, etc.), alloy composition (low alloyed steels, stainless steels, Ni-based super-alloys, Ti-alloys, etc.) and powder handling on the surface composition of the powder is summarized. A generic model of the oxide distribution depending on the alloy composition and manufacturing method is developed. Typically powder particles are covered by homogeneous oxide layer of the main alloying elements and particulate features, formed by stable high-temperature oxides.