Metal spray deposition of cylindrical preforms

A number of deposition experiments were carried out in a metal spray deposition facility for cylindrical preforms, at Sandvik Steel AB. Thick layers of modified Inconel 625 were sprayed over steel bars 170 mm in diameter and 8 m long. The rods were at room temperature during the deposition process. The effect of rotational velocity and fraction solidified in the spray was studied. Measurements of grain length intercept and porosity content were performed, as well as estimations of the shape of the actual deposition profile. Microprobe analysis was accomplished in different locations on the samples. A computational fluid dynamic model is implemented together with a continuum heat transfer model in order to facilitate the analysis. The range of the rotational velocity studied did not show any large effect on the formation of the base porosity. Three main zones were identified in the microstructure, i.e. porous-dendritic, transition and equiaxed. The segregation patterns suggested that a chemical homogenization occurred during the process. This was supported by the results of the numerical calculations.