Hardness variation in inconel 718 produced by laser directed energy deposition

Directed energy deposition (DED) of Inconel 718 is of critical importance for the repair of aerospace components, which have tight tolerances for certification, particularly on mechanical properties. Significant hardness variation has been seen throughout DED manufactured Inconel 718 components, suggestive of variation in mechanical properties, which must be understood such that the variation can either be removed, or implemented within the design in line with regulatory guidance. In this work, γʹ precipitation was theorised to be the cause of hardness variation throughout the component, despite Inconel 718 conventionally being regarded as a γʺ strengthened alloy. A simple precipitation potential model based on a moving heat source was found to correlate with the measured hardness and explain the hardness distribution observed. In addition, it has been shown that sections under a critical thickness of 2 mm never reach the peak hardness in the as-built condition. This understanding allows for the development of in-situ heat treatment strategies to be developed for microstructural, and hence, mechanical property optimisation, necessary for repair technologies where post processing steps are limited

Hardness variation in inconel 718 produced by laser directed energy deposition

Directed energy deposition (DED) of Inconel 718 is of critical importance for the repair of aerospace components, which have tight tolerances for certification, particularly on mechanical properties. Significant hardness variation has been seen throughout DED manufactured Inconel 718 components, suggestive of variation in mechanical properties, which must be understood such that the variation can either be removed, or implemented within the design in line with regulatory guidance. In this work, γʹ precipitation was theorised to be the cause of hardness variation throughout the component, despite Inconel 718 conventionally being regarded as a γʺ strengthened alloy. A simple precipitation potential model based on a moving heat source was found to correlate with the measured hardness and explain the hardness distribution observed. In addition, it has been shown that sections under a critical thickness of 2 mm never reach the peak hardness in the as-built condition. This understanding allows for the development of in-situ heat treatment strategies to be developed for microstructural, and hence, mechanical property optimisation, necessary for repair technologies where post processing steps are limited

On the Effect of Nb on the Microstructure and Properties of Next Generation Polycrystalline Powder Metallurgy Ni-Based Superalloys

Abstract The effect of Nb on the properties and microstructure of two novel powder metallurgy (P/M) Ni-based superalloys was evaluated, and the results critically compared with the Rolls-Royce alloy RR1000. The Nb-containing alloy was found to exhibit improved tensile and creep properties as well as superior oxidation resistance compared with both RR1000 and the Nb-free variant tested. The beneficial effect of Nb on the tensile and creep properties was due to the microstructures obtained following the post-solution heat treatments, which led to a higher γ′ volume fraction and a finer tertiary γ′ distribution. In addition, an increase in the anti-phase-boundary energy of the γ′ phase is also expected with the addition of Nb, further contributing to the strength of the material. However, these modifications in the γ′ distribution detrimentally affect the dwell fatigue crack-growth behavior of the material, although this behavior can be improved through modified heat treatments. The oxidation resistance of the Nb-containing alloy was also enhanced as Nb is believed to accelerate the formation of a defect-free Cr2O3 scale. Overall, both developmental alloys, with and without the addition of Nb, were found to exhibit superior properties than RR1000.This work was supported by the Rolls-Royce/EPSRC Strategic Partnership under EP/H022309/1, EP/H500375/1 and EP/ M005607/1

Controlling grain structure in metallic additive manufacturing using a versatile, inexpensive process control system

Abstract Additive manufacturing (AM), commonly termed 3D printing, is a revolutionary manufacturing technology with great industrial relevance in the aerospace, medical and automotive sectors. Metallic AM allows creation of complex intricate parts and repair of large components; however, certification is currently a concern due to lack of process consistency. A versatile, inexpensive process control system was developed and integrated, reducing variability in melt pool fluctuation and improving microstructural homogeneity of components. Remnant microstructural variation can be explained by the change in heat flow mechanism with geometry. The grain area variability was reduced by up to 94% at a fraction of the cost of a typical thermal camera, with control software written in-house and made publically available. This decreases the barrier to implementation for process feedback control, which can be implemented in many manufacturing processes, from polymer AM to injection moulding to inert-gas heat treatment

Research data supporting "The effect of heat treatment on precipitation in the Cu-Ni-Al alloy Hiduron130"

The data includes the raw files for all data reported in publication "The effect of heat treatment on precipitation in the Cu-Ni-Al alloy Hiduron 130". SEM, TEM, EDX, XRD xy file, DSC text files and hardness data is all included