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.

Particle size versus grain size relation in the sprayformed Al-18Si composites

Abstract: Various hypereutectic Al-18Si-X composites with different average Si particle sizes ranging from 0.2∼30 μm were produced by varying process parameters of spray forming. The effect of the Si particle size in determining the matrix grain size was investigated in order to design the optimum process for producing hypereutectic Al-18Si-X composites with fine microstructures. The experimental results suggested that the Si particle size greater than 2 μm is desirable for retarding the grain coarsening during subsequent forming processes, resulting in the fine microstructure. The observed results on the coarsening behavior of grains during spray-forming were analyzed from the free energy viewpoint.

Low Cost, Net Shape Fabrication of Rhenium and High Temperature Materials for Rocket Engine Components

Abstract: : Vacuum Plasma Spray techniques (VPS) have been developed to reduce the cost and fabrication time of metal and ceramic rocket engine components. Refractory metals and ceramics such as Re, Hf, W, W/Re, HfC, and HfN are being used for their high melting temperatures and chemical stability. However, the difficulty of forming these materials into complex shapes has limited their application in the past. The VPS technique involves spraying material onto a mandrel of the desired shape and subsequently removing the mandrel. A primary advantage of VPS forming over other powder metallurgy techniques is that near-net-shape spray forming of components significantly simplifies and reduces the cost of fabrication due to the high material utilization and reduction of laborious machining. Rocket nozzles have been fabricated and successfully tested in advanced applications with zero erosion. Standard metallurgical techniques have been used to characterize the effect of processing parameters on the microstructure of spray formed deposits. The deposited materials have high density with fine grain microstructures.

Microstructural Comparison of Spray-Formed and Conventionally Cast 2.5C–19Cr High-Chromium White Iron

Abstract: A billet of hypoeutectic high-chromium white iron (2.5% C, 19% Cr) was spray formed using gas-to-metal ratios of ~0.9, ~1.0, and ~1.1. The as-sprayed material was close to full density and contained fine (Fe,Cr)7C3 carbides (27–30 vol%) uniformly distributed in a matrix consisting of pearlite and ferrite. Length of the carbides rarely exceeded 30 μm. This was in stark contrast to a conventionally cast starting material, which contained coarse (Fe,Cr)7C3 carbides (~22 vol%) non-uniformly distributed in a matrix consisting of austenite and martensite. Length of the carbides in the cast material occasionally exceeded 100 μm. Varying gas-to-metal ratio between 0.9 and 1.1 did not result in any significant changes in carbide morphology, although slightly coarser carbide morphology was produced with the gas-to-metal ratio of 0.9. Regardless of the gas-to-metal ratio, the finest carbide morphology was found in the surface region of the spray-formed billet.

Modeling the in-flight events during metal spray forming

Abstract: In this work, the in-flight events occurring during deposition over a rotating substrate were modeled. The calculations were performed by solving the momentum and enthalpy equations for the gas. A Lagrangian approach was used to obtain the trajectories and thermal history of the droplets. A modified heat capacity model was used to simulate the release of latent heat due to the solidification of the droplets. Turbulent particle dispersion was not considered. The results showed that the droplet temperature strongly depends on the droplet diameter and on its location in the spray since the relative velocity between the gas and the droplets varies largely depending on the location. An estimation of the state of the spray is presented in terms of mass and thermal averages. The results showed that the average fraction of solid obtained in the spray depends on the initial conditions, such as gas temperature and particle size distribution parameters.