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.

Thermally Sprayed Prepregs for Advanced Metal Matrix Composites

Abstract: Advanced continuous fiber reinforced metal matrix composites (MMC) are manufactured using thermally sprayed prepregs and subsequent semi solid forming. The prepregs consist of fiber woven fabrics, which will serve as reinforcement and a thick metal alloy coating on top of the fabrics, which will serve as matrix material. The coated fabrics are trimmed to the shape of the component and laminated in packages of 40 to 80 prepregs to form a component. The prepregs are reheated into the semi- solid state of the alloy and can be solidified to a dense MMC with no residual porosity by semi- solid forging (thixoforging). The deposited alloy infiltrates the fabrics with 40% to 60% vol. liquid fraction. The fine- grained structure of the thermally sprayed metal coatings allows the required formation of globular grains during remelting and improves the impregnation behavior. Conventional thixoforming alloys achieve this structure by continuous casting with electromagnetic stirring or spray forming under inert gas atmosphere to form a massive billet rod, not suitable for infiltration of fiber structures. The thermal spray coating process is carried out under atmospheric conditions and allows the manufacturing of continuous reinforced MMC due to significant reduction of fiber damage. Chemical interaction and mechanical load on the fibers are minimized during processing due to a globular grain structure of the solid phase dispersed in the metal matrix melt, short flow paths during thixoforging, short cycle times and only a liquid fraction of 40% to 60% vol.. A production line to coat fiber fabric coils in a single continuous procedure is introduced to provide the MMC production with prepregs consisting of various reinforcement fiber materials and a wide range of metal matrix alloys capable for thixoforging densification.

Nozzle, vessel and spray forming.

Abstract: An improved nozzle which allows molten metals to be sprayed at low metal flow rates. This is useful for the Plasma Arc Melting process which used a hearth to prevent ceramic inclusions in the end product. The new nozzle design avoids metal freeze-off at the nozzle tip because a bore insert is positioned into a standard nozzle. The bore insert is a conduction heater, e.g., it is fabricated from boron nitride or the like. In use, molten metal is in contact with the insert so it maintains the insert at about the temperature of the molten metal; this then maintains the nozzle tip at a higher temperature than that of a standard nozzle. Freeze-off in the nozzle is non-occurring as long a molten metal is in the crucible.

Evaluation of porosity in spray deposited A2 tool steel

Abstract: The objective of the present study is to provide a numerical model to serve as a guide in the determination of optimum processing parameters for the spray forming of tool steels. Porosity is predicted using a heuristic model that incorporates the effect of the relative magnitudes of the fluid flow characteristic time and the solidification characteristic time on the porosity formation process, Two regimes, the 'fast flow' regime and the 'fast salidification regime, are identified a priori. Expressions for porosity as a function of the particle size distribution, the over-age solid fraction of the incident spray, and the solidification contraction are derived, based on these assumptions. The average solid fraction of the incident spray is estimated from the droplet size distribution and the solid fraction of a single droplet of a given size. The fatter is determined by cakulating the droplet dynamics and thermal history. The effects of process parameters (melt superheat, atomization pressure, deposition distance, and melt mass flow rate) on the level of porosity are investigated. By determining the conditions corresponding to a minimom in predicted porosity, optimum processing parameters can be assessed. As a result, processing maps are provided as a reference for achieving spray fermed tool steels with minimum parosity.

Manufacture of semi finished steel or nickelous system alloy

Abstract: PROBLEM TO BE SOLVED: To improve abrasion resistance property or mechanical properties by making it a semi finished item, wherein a nitrogen or a nitrogen contained gas is sprayed, after a given value of titanium is added to a steel which does not contain a titanium or a nickel system liquid alloy. SOLUTION: A billet is made by a spray forming of an alloy, wherein a titanium added volume is set to be 0.01-2.5 wt.%, preferably 0.1-1.0 wt.%, in a nitrogen gas atmosphere. Thus, a titanium nitride is formed, being dispersively precipitated as a fine precipitate, and a material character of the alloy is improved by restraining a growth of grain size, coarse graining at the time the billet is finally solidified and cooled. Specifically, after adding 1% Ti to a given liquid metal composition, for example, a molten alloy composed of C: 0.1%, Cr: 12%, Mo: 1.75%, Ni: 2.5%, V: 0.3%, the nitrogen gas is used as a double spraying device. A dropping which being partially solidified with the liquid is sprayed to a moving collector disc so as to make a billet in a range of diameter being 200-500 mm, and of 2 m length.

Advances in powder metallurgy - 1991. Vol. 5 - P/M materials; Proceedings of the Powder Metallurgy Conference and Exhibition, Chicago, IL, June 9-12, 1991

Abstract: The present volume powder metallurgy materials discusses the state of the PM industry, a metallurgical evaluation of new steel powders, design criteria for the manufacturing of low-alloy steel powders, and homogenization processing of a PM maraging steel. Attention is given to the corrosion resistance of full density sintered 316 SS, the performance characteristics of a new sinter-hardening low-alloy steel, wear performance of compositions made by low alloy iron/high alloy powder mixtures, and the strengthening of an AISI 1020 steel by aluminum-microalloying during liquid dynamic compaction. Topics addressed include the influence of alloying on the properties of water-atomized copper powders, fundamentals of high pressure gas atomization process control, advanced sensors and process control of gas atomization, and bimetallic tubulars via spray forming. Also discussed are factors affecting the delamination of PM molybdenum during stamping, applications of powder metallurgy molybdenum in the 1990s, and powder processing of high-temperature oxides.