Uniform Hot Compression of Nickel-based Superalloy 720Li under Isothermal and Low Friction Conditions

Abstract

Isothermal compression tests at 1 000°C and 0.1 s − 1 strain rate, in which mica or glass sheets were used as a lubricant, were conducted. Isothermal condition was achieved by placing high-heat-resistant (HHR) alloys between a workpiece and ceramic tools in the induction-heating configuration to prevent heat from escaping to the ceramic tools. To perform high compression tests, it was necessary to increase the diameter of the HHR alloy, for which a new single-turn coil was designed using FEM calculation coupled with deformation-temperature electromagnetic fields. In order to obtain the correct flow stress, inverse analysis was conducted using the FEM calculation, in which temperature and strain rate fluctuations were compensated. However, the compensation was insufficient when the distribution of temperature and strain rate was large. The use of glass sheets as a lubricant considerably reduced friction and uniform deformation was achieved. Thus, flow stress obtained using the inverse analysis became extremely reliable. The flow stress of mica obtained using inverse analysis with a constant friction coefficient was different from that of glass. Introducing new friction model that the friction coefficient changed from 0.02 to 0.3, the flow stress of mica was consistent with that of glass. Therefore, the flow stress obtained using the inverse analysis for the new configuration proposed in this study proved to be reliable.

Flow Curve of Superalloy 718 under Hot Forming in a Region of <i>γ</i>” Precipitation

“…The material parameters and other conditions of tool, mica, and intermediate layer 30) were applied to calculate the temperature distribution of specimen using thermomechanical CAE (Table 3). This method was presented in the previous study.…”

Molecular Dynamics Study on Nano-Friction and Wear Mechanism of Nickel-Based Polycrystalline Superalloy Coating

“…Figure 10 shows the different kinds of defects in the workpiece after the grinding ball rubs across the grain boundary. It can be seen from the Figure 10a is an atomic cluster [11], Figure 10b is a columnar dislocation defect [23], and Figure 10c is the stacking fault tetrahedron [25]. The reason is that with the increase of grinding heat caused by friction, the migration rate of atoms in the workpiece is accelerated and the defect atoms attract each other and stack tightly to form atomic clusters and columnar dislocation defects.…”

“…In addition, because the scale of cracks and wear marks in actual friction is only a few nanometers or smaller. It is difficult to observe dynamically through experiments [11,12]. In this context, the above process is realized by molecular dynamic (MD) simulation.…”

Influence of Microsegregation on the TiN Inclusions Formation Behavior in a K418 Superalloy during the Continuous Unidirectional Solidification Process

“…Nickel-based superalloys have been widely used for manufacturing key structural components in aircraft turbines due to their high good strength and excellent resistance to oxidation at elevated temperatures. [1][2][3][4] It is well known that nonmetallic inclusions in superalloys have been regarded as detrimental species that are harmful to the mechanical properties of cast products. [5][6][7] The formation of nonmetallic inclusions was generally caused by the addition of revert alloy, oxidation, and the precipitation during the solidification process.…”