Binder jet 3D printing—Process parameters, materials, properties, modeling, and challenges

Reconstruction of parent grains from EBSD data

This study examines the possibility of twinning to occur in Ti-6Al-4 V during moderate (4 - 14%) uniaxial compression at room temperature using a slow strain rate (10−6s−1). To do this, the starting material was manufactured to have strong basal texture components in the transverse and normal directions but not in the rolling direction. After only 6% compressive deformation parallel to the rolling direction it was possible to indentify a significant texture change introducing a strong basal texture component in the rolling direction. TEM analysis provided evidence of twins within grains, but at too low a volume fraction to explain the texture changes. Detailed EBSD mapping was carried out and showed an increasing number of entire grains to have their c-axis aligned with the loading direction in the deformed material, suggestive of entire grain twinning. The root cause for sudden complete grain twinning can only be speculated about at the moment, but it is suggested that the stress required for twin nucleation is significantly higher than that required for their propagation.

Deformation twinning in Ti-6Al-4V during low strain rate deformation to moderate strains at room temperature

A high strength high γ ′ fraction nickel-based superalloy powder RR 1000 has been hot isotatically pressed (HIPed) at different temperatures. Microstructural analysis and assessment of the tensile properties were performed on these samples. It was found that HIP led to the formation of (Hf,Zr)O 2 particles on prior particle boundaries (PPBs) which were not present in the as-received powder. It is suggested that the oxides are formed by the diffusion of Hf and Zr from the interior of powder particles to the particle surfaces where oxygen level is usually high. When different HIP temperatures were used, no obvious effect on oxide size and distribution was observed but there was an effect on the microstructure and tensile properties. Thus, HIPing at super-solvus temperatures reduced the density of PPBs over the density observed in samples HIPed at sub-solvus temperatures by making grains within the original powder particles grow beyond the precipitates on PPBs, resulting in larger grains with serrated boundaries. Slow cooling from HIPing temperatures also led to the formation of irregular-shaped γ ′. The 0.2% yield strengths at room temperature and at 700 °C were found to decrease with increase of HIP temperature but the high temperature ultimate tensile strengths and elongation increased considerably. Increasing HIPing temperature from sub-solvus to super-solvus temperatures also led to the transition of fracture mode from interparticle debonding to transgranular fracture mode.

Influence of hot isostatic pressing temperature on microstructure and tensile properties of a nickel-based superalloy powder

Influence of heat treatment on microstructure and tensile behavior of a hot isostatically pressed nickel-based superalloy

In order to reduce costs and increase the operating temperatures in aero-turboengines and space propulsion systems, net-shape or near net-shape production processes have been developed for static parts through HIPing (Hot Isostatic Pressing) of nickel base superalloys prealloyed powders. The presented results hereafter are related to the manufacturing processes and the mechanical properties (tensile, creep and LCF) characterisation. The effects of net shape surfaces and of surface conditioning have been investigated too. Examples of actual parts (CFM56 turbine casing and Vulcain rocket engine gas generator) illustrate the presentation. This study has confirmed the interest of this production route and future potential for development.

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Production of net-shape static parts by direct HIPing of nickel base superalloy prealloyed powders

Plastic deformation, damage and rupture of PM Ti-6Al-4V at 20 K under monotonic loading

Damage mechanisms at a microscopic scale of PM Ti-6Al-4V at 20 K

The invention relates to the field of propelling nozzles, and in particular to a device (105) for connecting a first segment (103a) and a second segment (103b) of a propelling nozzle, made of thermally dissimilar materials. Said device (105) includes at least one pin (106) and an eccentric socket (107). The pin (106) has a first axisymmetric surface (106a) intended for being inserted in a radial opening (108) of the first nozzle segment (103a) and a second axisymmetric surface (106b) which is eccentric relative to said first axisymmetric surface (106a). The eccentric socket (107) has an inner axisymmetric surface (107a) which matches the second axisymmetric surface (106b) of the pin (106), and an outer axisymmetric surface (107b), which is eccentric relative to said inner axisymmetric surface (107a) and intended for being inserted in a radial opening (110) of the second nozzle segment (103b). The present invention also relates to a method for using said device (105) for connecting two segments (103a, 103b) of a nozzle (3), as well as to a propelling nozzle (3) thus assembled and to a rocket engine (1) including same.

Device for connecting two segments of a propelling nozzle

A combustion chamber including a diverging portion. The combustion chamber extends along a longitudinal axis and includes a fluid injection system from which there extends in a downstream direction a wall presenting a throat and a diverging portion situated downstream from the throat. The chamber further includes a tubular element surrounding the wall at least in part and configured to take up most of forces generated during operation of the chamber on the downstream end of the wall to transfer the forces to a structure situated upstream from the chamber.

Didier Guichard

Papers

Production of net-shape static parts by direct HIPing of nickel base superalloy prealloyed powders

Plastic deformation, damage and rupture of PM Ti-6Al-4V at 20 K under monotonic loading

Damage mechanisms at a microscopic scale of PM Ti-6Al-4V at 20 K

Device for connecting two segments of a propelling nozzle

Combustion chamber provided with a tubular element