Improvement in the Microstructure and Tensile Properties of Inconel 718 Superalloy by HIP Treatment

Abstract

Hot Isostatic Pressing (HIP) is a process that uniquely combines higher pressure and temperature to produce materials and parts with substantially better properties than those by other methods. The aim of this paper is to discuss the methods and to find a suitable process of HIP for Inconel 718 superalloy. In this study, the HIP process parameters considered were; temperatures: 1423, 1448, 1453 and 1478 K, pressures: 100, 150, 175 and 200 MPa, and soaking times of 2, 3 and 4 hours. The Inconel 718 superalloy is used throughout this study. To evaluate the effects of microstructure and tensile properties of 718 alloy by HIP process, tensile test at two different strain rates at room and high temperature were evaluated. The microstructure, TEM and XRD inspections were performed.The experiment results show that at 1453 K, 175 MPa, 4 hours of HIP treatment for Inconel 718 superalloy was optimal. It can improve the microstructure and tensile properties of 718 castings. Through the optimal HIP treatment, the grain sizes are uniform and the segregated structure is improved. At fast strain rate (0.001 s À1 ), it increased the tensile strength by 31% at 298 K, 27% at 813 K, and 24% at 923 K. The 0.2% yield strength increased 40% at 298 K, 31% at 813 K, and 28% at 923 K. Meanwhile the elongation increased 100% at 298 K, 130% at 813 K, and 60% at 923 K after tension tests. When the strain rate was very slowly (0.0001 s À1 ), it also increased the tensile strength by 24% at 298 K and 20% at 813 K. The 0.2% yield strength increased 29% at 298 K and 27% at 813 K. The elongation increased 54% at 298 K and 282% at 813 K.

In situ TEM observation of γ′, γ″ and δ precipitations on Inconel 718 superalloy through HIP treatment

“…Most of the nickelbased superalloys use vacuum melting for production, however, segregation, porosity, and non-uniformity of the microstructure are problems generated during the solidification process and these defects degrade the mechanical properties of the alloys. HIP process can densify casting, indicating improvement of strength, ductility, and fatigue life with significantly less variation from lot to lot [22]. The HIP treatment showed an obvious increase in hardness to HRC 43.7 and a decrease of about 85.9% in porosity.…”

“…HIP treatment could enhance the effects of MC carbides and precipitation-strength ␥ phases [9,10]. The lump MC carbides, which appear within the grain boundaries, are helpful for the improvement of stress rupture life, and they can effectually prevent the grain-boundaries sliding [21][22]. Table 1 compares the hardness, properties, and average grain size of as-heat treated and HIP treated 718 alloy.…”

“…The specimen sizes of the tension test (CNS 2112 G2014) are shown in Fig. 1 In earlier studies, Chang et al reported the effects of different parameters of HIP treatments for 718 alloy [19][20][21][22]. The key parameters of the HIP process include temperature, pressure, and soaking time.…”

Numerical Simulation of Surface Modification During Machining of Nickel-based Superalloy

“…where d is the average grain size, and a and k are two constants calibrated from literature [10][11][12]. Experimental results on cutting forces, chip morphology and temperature are used to validate the results of the orthogonal cutting simulation of Inconel 718.…”

Effects of HIP Treatment on the Microstructure of Cr50-Si50 Target

“…HIP consolidates powders of metals, ceramics, carbides into fully dense, complex parts with net or near net shapes. [15][16][17] The aim of this paper is to discuss the methods and to find a suitable temperature of HIP treatment for Cr50-Si50 target. Otherwise, we also to find the effects of microstructure on the mechanical properties of HIP treated Cr50-Si50 target.…”