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The spray forming process combines the benefits of rapid solidification processing with the cost advantages associated with near net shape processing. High pressure gas impinges on a stream of molten metal and atomises it into an array of fine droplets. The gas then accelerates these droplets towards a moving substrate where they are collected and a near net shaped preform is formed incrementally. Preforms may have billet, tube or strip geometries depending on the configuration of the substrate manipulation system. This paper will describe and discuss the key stages of the process of gas atomisation, droplet flight, deposition and microstructural evolution, and will highlight current knowledge and recent advances. It will also address the future directions of research and development. An important technological requirement, for instance, is increased yield through the reduction of over-sprayed powder and the control of preform shape. Of particular scientific interest is the evolution of the equiaxed grain structure typical of spray formed materials. |
