Assessment of Boron Diffusivities in Nickel Borides by Two Mathematical Approaches

In the work of this contribution, two kinetics models have been employed to assess the boron diffusivities in nickel borides in case of Inconel 718 alloy. The first approach, named the alternative diffusion model (ADM), used the modified version of mass conservation equations for a three-phase system whilst the second one employed the mean diffusion coefficient (MDC) method. The boron diffusivities in nickel borides were firstly evaluated in the interval of 1123 to 1223 K for an upper boron concentration of 11.654 wt% in Ni4B3. The boron activation energies in the three phases (Ni4B3, Ni2B and Ni3B) were secondly deduced by fitting the values of boron diffusivities with Arrhenius relations. Finally, these values of energy were compared with the results from the literature for their experimental validation.

Analysis of control factors and surface integrity during wire-EDM of Inconel 718 alloy using T-GRA approach

In today’s competitive modern manufacturing sectors, there is a vital need of utter precision and rigorous processing using various manufacturing approaches that directly influences the cost and processing duration of mechanized materials in addition to the consistency of the finished products. Therefore, it’s essential to figure out the required output by adjusting the control factors of any machining techniques which resulted in optimal values of the desired outcome. In this study, machining evaluation and process optimization is carried out on volumetric extraction of material namely material removal rate (MRR), kerf obtained during the machining (KW) and surface roughness (SR) of Inconel 718 superalloy during CNC controlled wire- electrical discharge machining. Four controllable factors- pulse interval, wire speed, pulse duration and peak current are considered to investigate the influence on performance measures. Taguchi's L16 has been used to construct the set of experiments before physical experimental runs and most influencing factors have been evaluated using ANOVA. SEM images and EDXS analysis have been resorted to examine the morphology of Inconel 718. These findings assist in identifying the topography of the machined surface. Further, the optimum integration has been obtained for the best yield and recorded using grey relational analysis integrated with Taguchi’s technique (T-GRA). The unfamiliarity of the work is based on consideration of zinc coated thin wire electrode and Taguchi-Grey combined approach of modelling with four levels of experimental design.

Study of Microstructure and Mechanical Properties of As-built and Heat-treated Additive Manufactured Inconel 718 Alloy

Additive manufacturing technology is becoming popular in the industry because it allows the manufacturer to fabricate cost-effective, strong, lightweight, and complex-shaped parts directly from 3D design data as compared with the conventional manufacturing method. Inconel 718 alloy is the most demanding material in aviation as well as in the automobile industry, in terms of manufacturing high-performance parts. In this study, Inconel 718 samples were built using the direct metal laser sintering process, and standard heat treatment was performed on the samples to improve their microstructure and mechanical properties. The as-built samples exhibited good grain structure with fine laves phases, but the matrix was free from ?' and ?" phases. During the heat treatment, the strengthening phases ?' and ?" precipitated. The mechanical properties of as-built and heat-treated samples were analysed and compared. Tensile tests revealed that the direct-aged sample had the higher tensile strength compared with the other conditions, whereas the as-built samples had higher ductility. Finally, fractography and microstructure analysis were performed to measure the failure modes of tensile specimens.

Interfacial Characteristics and Mechanical Properties of CuSn15/HT250 Prepared via Additive Manufacturing Combined with an Inconel 718 Interlayer

Tremendous discrepancies in the positive enthalpy of mixing and the coefficient of thermal expansion emerge between the copper alloy and the gray cast iron, accounting for numerous pores and cracks in the interfacial region during the metallurgical bonding process. To enhance the interfacial bonding properties of these two refractory materials, laser-directed energy deposition was applied to fabricate the CuSn15 alloy on the HT250 substrate; meanwhile, Inconel 718 alloy, acting as the interlayer, was added to their bonding region. Firstly, the effect of the deposition process on deposition layer quality was investigated, and then the effects of Inconel 718 addition on the interfacial morphology, element distribution, phase composition, bonding strength, microhardness were studied. The results showed that a substrate (HT250) without cracks and a deposition layer (CuSn15) free from pores could be obtained via parameter optimization combined with preheating and slow cooling processes. Adding the Inconel 718 interlayer eliminated the interfacial pores and cracks, facilitated interfacial element (Cu, Fe, Ni) diffusion, and enhanced interfacial bonding strength. The interface between HT250 and CuSn15 mainly contained the FeSn2 phase, while the interfaces of the CuSn15-Inconel 718 and the Inconel 718-HT250 were mainly composed of the Ni3Sn4, Cr5Si3, FeSi2, Cr7C3. The microhardness and fracture morphology of the interfacial region in the samples with and without the interlayer were also studied. Finally, CuSn15 was also successfully deposited on the surface of the HT250 impeller with large size and complex structure, which was applied in the root blower.