Microstructure development during spray casting

Abstract

Spray casting is emerging as an attractive technology for the production of net or near-net-shaped components of a variety of materials. The process (e.g. the OspreyTM process) involves sequential atomization and droplet consolidation at deposition rates in excess of 0.25kg/s. It is possible to fabricate axisymmetric shapes such as disks, billets, tubes and sheet or strip, by suitably manipulating substrate configuration and motion. A major advantage of spray casting is that the product has a uniform distribution of equiaxed grains (20μm-200μm), no macroscopic segregation of alloying elements, a uniform distribution of second phases, and low oxide content. In this paper, the scientific aspects of the development of microstructure during spray casting are reviewed. Successful utilization of spray casting mandates control of preform shape with accompanying metallurgical integrity. Consequently, it is a critical to quantify the contribution of the mechanisms involved in the formation of preform shape, microstructure and overall yield.