Spray forming

About: Spray forming is a research topic. Over the lifetime, 1153 publications have been published within this topic receiving 12869 citations. The topic is also known as: spray casting & spray deposition.

Solidification microstructure and M2C carbide decomposition in a spray-formed high-speed steel

Abstract: The solidified carbide morphology, the decomposition behavior of the M2C carbide, and the carbide distribution after forging of an Fe-1.28C-6.4W-5.0Mo-3.1V-4.1Cr-7.9Co (wt pct) high-speed steel prepared by spray forming have been investigated. The spray-formed microstructure has been characterized as a discontinuous network of plate-shaped M2C carbides and a uniform distribution of fine, spherical MC carbides. The metastable M2C carbides formed during solidification have been fully decomposed into MC and M6C carbides after sufficient annealing at high temperatures. Initially, the M6C carbides nucleate at M2C/austenite interfaces and proceed to grow. In the second stage, the MC carbides form either inside the M6C carbides or at the interfaces between M6C carbides. With this increasing degree of decomposition of the M2C carbide, the carbides become more uniformly distributed through hot forging, which produces a significant increase in ultimate bend strength. The decomposition treatment of M2C carbide has been found to be most important for obtaining a fine homogeneous carbide distribution after hot forging.

Microstructure and mechanical properties of Al–Si alloys produced by spray forming process

Abstract: The microstructural characteristics and mechanical properties of Al–6.5Si and Al–18Si alloys have been investigated. The alloys were spray-deposited and hot extruded at 480°C with an area reduction ratio of 6:1. The microstructure of the spray-deposit of Al–6.5Si alloy showed spherical morphology of the primary α-phase with a globular shape of the eutectic Si phase in the inter-particle boundaries. On the other hand, a fine particulate morphology of primary Si phase uniformly dispersed in the matrix of the α-phase was observed in spray-deposit of Al–18Si alloy. Microstructural refinement was further increased in the hot extruded alloys. The room temperature tensile tests of spray formed and extruded alloys showed considerable increase in their strength and ductility over that of the as cast alloys. The improvement in mechanical properties of spray formed alloys is discussed in light of the microstructural modifications induced during spray deposition process.

Modelling of droplet dynamic and thermal histories during spray forming—II. Effect of process parameters

Abstract: A computer model has been developed to describe the in-flight dynamic and thermal histories of gas atomised droplets as a function of distance during spray forming. The model has been used to investigate the effects of the dynamic and thermal behaviour of individual gas atomised droplets and the cooling and solidification behaviour of the overall spray. The most influential parameters for a given alloy system, in order of importance, are: (i) droplet diameter and, therefore, the droplet size distribution within the spray; (ii) initial axial gas velocity at the point of atomisation and the subsequent gas velocity decay profile; (iii) melt mass flow rate; (iv) melt superheat at the point of atomisation; and (v) alloy composition. Experimental measurements of gas velocities and droplet size distributions during spray forming allow the spray solid fraction at deposition to be calculated and used in a subsequent computer model of billet heat flow to predict the billet top surface temperatures and solid fractions.