The process characteristics of the twin-nozzle-scanning spray forming were introduced in the paper briefly. Additionally, the microstructure of high-speed steels produced by spray forming was inspected using scanning electron microscopy (SEM, back diffraction morphology) and energy dispersive spectroscopic analyses (EDS). Without thermal isotropic pressure (HIP) and hot forge, at some position of spray deposited HSS billet some porosity was found, the forming reason of porosity was analyzed.

Analysis of Twin-Nozzle-Scanning Spray Forming Process and Spray Formed High Speed Steel (HSS)

Methods are provided for producing alloy forms from alloys containing one or more extremely reactive elements and for fabricating a component therefrom. The fabricating method comprises substantially removing a reactive gas from the fabrication environment. An alloy form of the alloy is formed. The alloy form is formed by melting the alloy or by melting one or more base elements of the alloy to produce a molten liquid and introducing the one or more extremely reactive elements into the molten liquid. The molten alloy is shaped into the alloy form. The component is formed from the alloy form. If the one or more extremely reactive elements are introduced into the molten liquid, such introduction occurs just prior to the shaping step.

Methods for producing alloy forms from alloys containing one or more extremely reactive elements and for fabricating a component therefrom

A numerical study of the deposition dynamics of twin-atomizer spray-forming of large-diameter billets is presented with a focus on the coupled effect of the twin-atomizer scan frequency and substrate rotation frequency. The common period of the two frequencies ξ was the dominant parameter to govern the deposited droplet mass and billet shape. When ξ ≥ 10, a uniform mass distribution at the deposition surface was predicted, and the calculated shape agreed with experiments.

Modeling the Deposition Dynamics of a Twin-Atomizer Spray Forming System

Compared with optical black, few attempts have focused on achieving broadband microwave blackbodies. In this study, all‐ceramic metamaterial microwave blackbodies are created by integrating a graded Gyroid shellular (GGS) metastructure design with additive manufacturing of polymer‐derived SiOC (PDCs‐SiOC) ceramics encapsulated by Si3N4 (SiOC@Si3N4). Hardly influenced by the destructive interference effect, as‐fabricated GGS‐structured SiOC@Si3N4 microwave blackbodies demonstrate a broadband microwave absorption (MA) above 83.6% (91.3% on average) across the entire X‐Ku band and encompassing higher frequencies above 18 GHz as well, together with the temperature insensitivity from room temperature to 500 °C. Based on the flexible electromagnetic tunability of PDCs‐SiOC, exceptional structural scalability is experimentally validated for metal‐doped modified CuSiOC and CoSiOC substrates with the same GGS metastructures, retaining high‐efficiency MA capability. Furthermore, attachment of perfectly reflecting metal backplanes further enhances the MA performance, with an ultrawide MA exceeding 67.9% (89.1% on average) achievable at 2.95–18 GHz for CoSiOC substrate. Meanwhile, the GGS‐structured SiOC@Si3N4 metamaterials possess additional multifunctional properties, such as good noise reduction performance as well as ultrahigh wear resistance. As a proof of concept, this study provides important guidance on achieving multifunctional coupling broadband MA characteristics by fully tapping the application potential of existing materials.

Multifunctional Metamaterial Microwave Blackbody with High‐Frequency Compatibility, Temperature Insensitivity, and Structural Scalability

The hot deformation behaviors of spray formed superalloy GH738 were investigated by using of Gleeble-3500 simulator in the temperature range of 950~1200, with a strain rate of 0.13~6.5s-1 and reduction of 50%. The corresponding flow curves were determined and hot deformed microstructures were observed. The results showed that the flow stress decreased with increasing deformation temperature or decreasing strain rate. A full dynamic recrystallization microstructures with fine-equiaxed grains were obtained at the temperature of 1100~1150 and strain rate of 2.6~6.5s-1. The hot deformation activation energy Q was 580.81kJ.mol-1, and the constitutive equation was derived by means of linear regression.

Constitutive Characteristic of Hot Deformation for Spray Formed Superalloy GH738

A unique pilot low-pressure spray forming plant was established and its spray atomisation and deposition process developed to study the new processing methods for high performance materials and to develop spray forming technology suitable for making sound superalloy preforms The results indicated that high density (>99%) preforms (billets and rings) with little gas pick-ups and with the microstructural features of rapidly solidified superalloys, ie refined equiaxed grains and uniform microstructure, could be achieved after the optimisation of the spray atomisation and deposition process The effects of subsequent thermal processing on the density, microstructure and mechanical properties of the spray formed superalloy were investigated Compared to the turbine disks and rings made by wrought superalloys, the spray formed superalloys with identical chemistry showed significantly improved metallurgical quality, higher mechanical properties, and better hot workability

Spray Forming and Thermal Processing for High Performance Superalloys

Continuous Si3N4 fiber reinforced SiNO matrix composites (Si3N4 f/SiNO composites) were innovatively prepared for long-time high-temperature resistant wave-transparent materials of hypersonic aircraft. The microstructure, high-temperature mechanical and dielectric properties of Si3N4 f/SiNO composites were investigated in detail. The as-fabricated Si3N4 f/SiNO composites have homogeneous SiNO matrix distribution for the special winding process, which is beneficial for the mechanical strength and wave-transparent properties. The average tensile strength and flexural strength at room temperature is 87.8 MPa and 171.2 MPa respectively, which suggests Si3N4 f/SiNO composites have excellent mechanical strength. The tensile strength value decreases to 54.6 MPa after heat-treated at 1000 ℃ for the surface reactions between the SiNO matrix and Si3N4 fibers. After heat-treated at 1550 ℃, the composites have the tensile strength value of 24.2 MPa for the high strength retention rate of Si3N4 fibers at this temperature. Si3N4 f/SiNO composites have excellent room temperature dielectric properties and excellent dielectric stability in different frequency bands (7–18 GHz). The dielectric constant values vary from 3.69 to 3.75 while the dielectric loss attains the order of 10−3. The dielectric constants and dielectric loss of Si3N4 f/SiNO composites are relatively stable from RT to 800 ℃. The as-fabricated Si3N4 f/SiNO composites that have excellent high temperature resistance and dielectric properties are the ideal high temperature wave-transparent composites. 

Microstructure, High-temperature Mechanical and Dielectric Properties of Novel Si3N4f/SiNO Wave-transparent Composites

Sound billets were produced at BIAM with a twin-scanning spray forming facility. Microstructure and mechanical properties of In718 alloy produced with this technology were examined. Both tensile strength and stress rupture properties are excellent with the rupture life even doubled after received a direct aging heat treatment.

Rui Ping Yao

Papers

Spray Forming and Thermal Processing for High Performance Superalloys

Microstructure, High-temperature Mechanical and Dielectric Properties of Novel Si3N4f/SiNO Wave-transparent Composites

Microstructure and mechanical properties of In718 alloy produced with twin-scanning atomizer