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.

Method of spray forming readily weldable and machinable metal deposits

Abstract: A method of spray forming a weldable metal deposit. The method comprises (a) providing a ceramic spray forming pattern, (b) heating the spray forming pattern to a sustained temperature sufficient to prevent internal stress formation in deposited carbon steel having a carbon content of less than about 0.3 weight percent when deposited on the heated spray forming pattern, (c) spraying metallic particles onto the spray forming pattern heated to the sustained temperature, and (d) allowing the sprayed metallic particles to cool to form a metal deposit. The metallic particles have a carbon content which is sufficient to result in metal particles having a carbon content of less than about 0.3 weight percent when deposited on the heated spray forming pattern. The resulting deposit has a carbon content of less than about 0.3 weight percent.

Influence of heat treatment on the microstructural evolution and mechanical properties of W6Mo5Cr4V2Co5Nb (825 K) high speed steel

Abstract: Spray forming (SF) is a newly developed rapid solidification and near-net-shape technique for preparing high-speed steels (HSSs) in recent years. However, a large amount of overspray powders will be produced in the SF process, which brings about a serious material pollution and waste. To solve this problem, a new method of the two-step sintering and subsequent heat treatment was used to fabricate high-performance W6Mo5Cr4V2Co5Nb (825 K) HSSs using the overspray powders. The microstructural evolution and mechanical properties by the heat treatment were systematically studied. Results show that near full dense 825 K alloys with many uniformly distributed carbides are obtained by the two-step sintering. After quenching and triple tempering, the alloys consist of the martensite, M6C and MC carbides, and a small amount of retained austenite. The carbides have smaller particle size of less than 3 μm and greater sphericity than the as-sintered alloy. The diffusion of alloying elements determines the dissolution and re-precipitation of carbides. The fabricated 825 K alloy quenched at 1180 °C and triple tempered at 540 °C possesses the best mechanical properties, with a hardness of 64.2 HRC and bending strength of 2858 MPa, which is much higher than that of casting alloy with similar composition. This work provides a feasible way to recycle the overspray powders.

Low-pressure spray forming of 2024 aluminum alloy

Abstract: In this paper, a newly developed low-pressure spray forming (LPSF) technique is described. The experimental results obtained with an as-deposited 2024 aluminum alloy are reported. It is shown that the application of reduced pressure significantly decreases porosity as compared to conventionally spray-formed 2024 aluminum alloy. Moreover, the resultant microstructures are similar to those achieved with conventional spray forming. The mechanisms of porosity formation in deposited materials, obtained using both low pressure and conventional spray forming, are discussed. Gas entrapment and interstitial porosity are proposed to be the two major sources of the porosity present in the as-deposited materials. On the basis of the present study, the controlled low-pressure environment during LPSF appears to influence the droplet trajectories and the gas flow field, leading to flow-straightening effects which result in significant reduction of porosity in the deposited materials.

Microstructural control by spray forming and wear characteristics of a Babbit alloy

Abstract: The effect of process variables during spray forming of a commercial Babbit alloy containing Pb74–Sn12–Sb11.5–Cu1.25–NiO.75–Cd0.3–As0.2 on its microstructure and wear characteristics were investigated. Variation in atomization gas pressure from 0.6 to 1.2 MPa and nozzle to substrate distance from 0.2 to 0.4 m revealed considerable change in the nature of porosity and microstructural features of the spray deposits. The process variables during spray deposition were optimized to achieve microstructural homogeneity and refinement in second phase particles of this alloy. The wear study of both the spray formed and as-cast alloy under an applied load of 10 to 70 N and sliding velocity of 0.2 to 1.5 ms-1 indicated two distinct regimes of mild and severe wear. In both the regimes, the spray-formed alloy consistently indicated a low wear rate compared to that of the as-cast alloy. In addition, the mild wear regime of the spray-formed alloy was extended to higher load and sliding velocity. Wear characteristics of the spray formed alloy is discussed in light of its microstructural features induced during spray deposition processing.