Fabrication of highly compact Inconel 718 alloy by spark plasma sintering and solution treatment followed by aging

The use of powder metallurgy for near net shape sintering of superalloy could lead to major savings in machining time and material. The main challenge in sintering Inconel 718 is to avoid the formation of a prior particle boundary (PPB) network that is deleterious to the mechanical properties. Using the Spark Plasma Sintering (SPS) technique, it is believed that Inconel 718 powders could be sintered without forming a PPB network due to the fast heating rate achieved and the reported cleaning effect of particle surfaces by the interparticle arc discharges. In this study, Inconel 718 was consolidated to near-full density at 1200°C under 50 MPa of pressure with heating rates ranging from 20°C/min to 800°C/min. The densification behavior of the powder was studied through the analysis of the densification curves and observation of the microstructure evolution from interrupted tests. The fast densification of Inconel 718 in SPS was linked to the formation of a supersolidus liquid phase due to the nature of the heating in this technique.

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Enhancing Mechanical Properties of the Spark Plasma Sintered Inconel 718 Alloy by Controlling the Nano-Scale Precipitations

Materials ◽

10.3390/ma12203336 ◽

2019 ◽

Vol 12 (20) ◽

pp. 3336

Author(s):

Shuaijiang Yan ◽

Yun Wang ◽

Qingxiang Wang ◽

Chengsong Zhang ◽

Dazhi Chen ◽

...

Keyword(s):

Electron Microscopy ◽

Mechanical Properties ◽

Heat Treatment ◽

Solid Solution ◽

Inconel 718 ◽

Production Efficiency ◽

Solution Treatment ◽

Inconel 718 Alloy ◽

Direct Aging ◽

Spark Plasma

The present study aimed to optimize the phase constituents and mechanical properties of the spark plasma sintered (SPS) Inconel 718 (IN718) alloy. A series of heat treatment routes were designed based on the phase relations in IN718 and performed for the optimization. The microstructure and phase compositions of the SPS IN718 alloys were examined by using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy disperse spectroscopy (EDS), and transmission electron microscopy (TEM). The mechanical properties of the samples were characterized at room temperature and at 650 °C. The results showed that large amounts of γ” (Ni3Nb) and γ’ (Ni3(Al, Ti)) strengthening phases precipitated in the IN718 alloy after direct aging (DA) of the as-fabricated sample. Moreover, the mechanical properties of the DA sample were comparable to that of the best one of the solution-treated and aged counterparts. The analysis showed that the rapid sintering and solid solution treatment of the IN718 alloy were achieved simultaneously by SPS. In the case of the SPS IN718 material, the direct aging regime had the same heat treatment effect as the conventional solid solution and aging treatment. This contributes toward improving the production efficiency and reduces manufacturing costs in the actual production process.

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