Showing papers on "Inconel published in 2023"

A new force-depth model for robotic abrasive belt grinding and confirmation by grinding of the Inconel 718 alloy

Abstract: Robotic abrasive belt grinding has been successfully applied to the grinding and polishing of aerospace parts. However, due to the flexible characteristics of robotic abrasive belt grinding and the time-varying characteristics of the polishing contact force, as well as the plastic and difficult-to-machine material properties of Inconel 718 alloy, it is very difficult to control the actual removal depth and force of the polished surface, which brings great challenges to robot automatic polishing. Therefore, the relationship between the grinding force and the grinding depth in the robotic abrasive belt grinding is analyzed in detail, the robot machining pose error model considering the deformation of the grinding head is established, and the Inconel 718 alloy machining experiment of the robotic abrasive belt grinding is designed. The mapping relationship between the grinding force and the grinding depth is obtained, and the grinding force ratio in the downgrinding and upgrinding mode is discussed. The experimental and theoretical comparisons results show that with the increase of the grinding depress depth, both the grinding depth and the grinding force show an irregular increasing trend, and the increasing trend of the grinding force (increases by about 344.44%–445.45%) is obviously greater than that of the grinding depth (increases by about 52.94%). When the grinding depress depth is large (greater than 3 mm), the feed direction force and the normal force appear obvious secondary pressure peaks at the beginning and end of grinding, which has not been seen in previous studies. In addition, regardless of whether it is downgrinding or upgrinding, the grinding force ratio decreases with the increase of the depress depth, and the grinding force ratio of downgrinding (average 0.668) is smaller than that of upgrinding (average 0.724). This study provides a reference for robotic abrasive belt grinding, and the surface quality of Inconel 718 alloy of robotic abrasive belt grinding can be further improved through the optimization of force and depth.

Outstanding strength-ductility synergy in Inconel 718 superalloy via laser powder bed fusion and thermomechanical treatment

Abstract: Addressing the strength-ductility dilemma in Inconel 718 superalloy using traditional strengthening strategies is a challenging. Here, based on the unique initial microstructure resulting from laser powder bed fusion (LPBF), we proposed a novel strategy that combines the LPBF with a subsequent thermomechanical treatment to simultaneously improve the strength and ductility of Inconel 718, having an architecture of abundant annealing twins at a finer grain size and coherent nano-precipitates (γ", γ'). The CR-A5-DA specimen exhibits mechanical properties with a yield strength of 1563.1 ± 10.5 MPa, tensile strength of 1759.7 ± 11.6 MPa, and maintained a favourable tensile elongation of 17.3 ± 0.8%. The outstanding strength-ductility synergy is mainly attributed to the amplification of effects, such as finer grains, intricate interactions between microstructures (twins + disperse nano-precipitates) and dislocations, driven by LPBF and thermomechanical treat. Meanwhile, the dynamic Hall-Petch effect and additionally strengthened microstructures induced by tensile loading, including nanotwins, stacking faults and Lomer-Cottrell locks, further improve the work hardening ability. This study presents a novel idea for the production of metal structural materials with a high strength-ductility synergy and broadens the scope of applications for additive manufacturing.

Effect of laser cladding parameters on Inconel 718 coating performance and multi-parameter optimization

Abstract: • Laser power had the most importance on the yield strength, UTS, and elongation. • Powder feeding rate had the most importance on the microhardness and yield strength. • Scanning speed had the most importance on the maximum load value. • Optimal process parameters for the laser cladding coatings were identified. • The reduction of the Laves phase might be the main reason for the improvement of coating performance after optimization. The purpose of this study is to improve the quality of the multi-track laser cladding coating. The Taguchi-Grey relation method was selected to realize process parameter optimization. The Taguchi method is used to design an L 16 orthogonal experiment. The influence of three important laser cladding parameters (laser power, powder feeding rate, and scanning speed) on the micro-hardness, maximum load value, yield strength, UTS, and elongation had been analyzed based on the analysis of variance (ANOVA) and signal to noise ratio (SNR) methods. The results showed that the yield strength, UTS, and elongation were significantly affected by the laser power; the powder feeding rate denoted a highly significant influence on the microhardness and yield strength; and the scanning speed was a highly significant factor that had an influence on the maximum load value. Then, grey relational analysis (GRA) was used to convert five response targets into a single grey relational grade (GRG) that could be quantified in order to optimize the parameters for maximum micro-hardness, maximum load value, yield strength, UTS, and elongation. Finally, the optimum cladding process parameters were obtained. Through analysis of microstructure, the reduction of the Laves phase might be the main reason for the improvement of coating performance after optimization.

Effect of precipitated phases on the mechanical properties and fracture mechanisms of Inconel 718 alloy

Abstract: In this study, hot-rolled Inconel 718 alloys were subjected to three different heat treatment schedules to develop various precipitated phases (γ″ phase, γ′ phase, needle-shaped δ phase, and granular δ phase). Based on microstructural characterization and mechanical testing, the effects of these precipitated phases on the mechanical properties and fracture mechanisms were investigated. The results showed that a double-aging treatment process was the key to ensuring the complete precipitation and growth of the γ″ and γ′ phases. A small amount of δ phase (∼2.5%) precipitating in the solution treatment stage did not affect the precipitation of the γ″ and γ′ phases in the subsequent aging treatment stage. An Inconel 718 alloy without δ phase precipitation had excellent impact toughness, and the fracture mode was ductile fracture caused by dislocation slip separation. However, if it was present, the morphology of δ phase determined the effect on the impact toughness. The fracture mechanism changed from a mixed fracture mode of intergranular and transgranular fracture to quasi-cleavage fracture when the morphology of the precipitated δ phase was transformed from needle-shaped to granular-shaped. According to the theory of the dihedral angle (2θ) for precipitated phase morphologies, a quantitative relationship between the interfacial energies of the needle-shaped δ phase and granular δ phase was determined. The interfacial energy of the needle-shaped δ phase was only ∼76% of that of the granular δ phase, meaning that the needle-shaped δ phase was likely to debond readily from the matrix, resulting in the formation of intergranular cracks.

Improvement in strength and ductility of rotary friction welded Inconel 600 and stainless steel 316L with Cu interlayer

Abstract: The objective of this work is to investigate the effect of Cu interlayer on the tensile strength and ductility of the rotary friction welded Inconel 600 and stainless steel 316 L joints, in welded and annealed conditions. Joints were made with and without Cu interlayer. The temperature and forces were recorded during rotary friction welding. The welded and annealed joints were subjected to tensile tests, microstructural analysis and fractography of fractured surfaces from tensile test samples. Microstructural observation at the joint interface revealed the elemental diffusion with minimal bulk intermixing of the base materials. The dynamic recrystallization led grain refinement was observed on the steel side and grain coarsening was noticed on the Inconel side, near the interface. A substantial severe plastic deformation zone was noticed in the interlayer region for the joint made with Cu interlayer. The strength and ductility of the joints with interlayer were 10.8% and 82.3% higher than the joints made without interlayer. Upon annealing, joint ductility improved by 14.2% and 8.8% for the joints made without and with interlayer, respectively.

Ultrasonic Vibration Assisted Turning of Inconel 825: An Experimental Analysis

Abstract: ABSTRACT In this experimental analysis, ultrasonic-vibration-assisted-turning (UVAT) is introduced to machine Inconel 825 using TiAlN coated WC insert. Different turning conditions (varying ultrasonic power intensity, feed rate and cutting speed) are generated using response surface methodology. Turning performances like cutting force (Fc), temperature (T) and surface roughness (Ra) were analyzed through invasive weed optimization to distinct the critical turning parameter. Fc, T and Ra have been decreased by 34.99%, 20.61% and 24.73% in UVAT than CT, due to intermittent motion of the cutting tool. It minimizes the contact time between tool and workpiece, helps in better heat dissipation during machining and relieves excessive stress developed at tooltip that enhances tool life. TiAlN coating further curtailed the friction between tool-workpiece interfaces, improving surface quality, reducing stress, temperature and wear on the tool. Tool wear and chip morphology is analyzed with SCM, and XRD is utilized to identify crystallographic analysis and residual stress..

Structure and durability evaluation of blast furnace slag coatings and thermal barrier coatings (TBCs) under high temperature conditions

Abstract: A high temperature aggressive environment is a great challenge for the long lifetime of thermal barrier coatings (TBCs). In this study, the hot corrosion and isothermal oxidation behavior of blast furnace slag (BFS) and yttria stabilized zirconia (YSZ) coated TBC systems were systematically investigated under high temperature conditions. This study aims to analyze the evaluation of microstructural properties of thermally sprayed CoNiCrAlY/BFS and CoNiCrAlY/YSZ coatings before and after high temperature oxidation and hot corrosion tests. For this purpose, the coatings were isothermally oxidized at 900 °C for 8, 24, 50, and 75 h. Hot corrosion behavior of CoNiCrAlY/BFS and CoNiCrAlY/YSZ coatings deposited on Inconel 718 superalloy substrates were studied at 900 °C in a Na2SO4 and V2O5 molten salt environment. CoNiCrAlY/BFS and CoNiCrAlY/YSZ TBC systems exposed to Na2SO4+ V2O5 molten salt at 900 °C investigate the hot corrosion behavior. The microstructure of coatings, formation of thermally grown oxide (TGO) layer, and degradation of coatings during isothermal oxidation and hot corrosion conditions were investigated. The oxidation and hot corrosion mechanisms were discussed. BFS, could be a potential alternative for the YSZ ceramic top coating in TBCs. The TBC system with BFS can be preferred for oxidation damage due to its low cost. YSZ and BFS TBCs are highly resistant to Na2SO4 and V2O5 molten salt environment.

Effect of heat treatments on Inconel 625 fabricated by wire and arc additive manufacturing: an in situ synchrotron X-ray diffraction analysis

Abstract: The effect of heat treatments on wire and arc additively manufactured Inconel 625 parts was investigated using in situ synchrotron X-ray diffraction and hardness testing. As-built samples revealed the presence of a γ-matrix with precipitation of γ′, γ′′ and MC carbides. When heat treated at 750°C for 4 h, γ′′ phase precipitated increasing the hardness by 5%. In situ X-ray observations revealed that heat treating at 870°C for 1 h resulted in δ-phase precipitation. Two different second-stage temperatures were tested (1050°C and 1150°C), which dissolved the δ-phase while MC carbides formed upon cooling. The second stage at 1150°C had a higher deleterious effect than the one performed at 1050°C due to extensive grain growth.

Dissolution kinetics of Laves phase during homogenization heat treatment of additively manufactured Inconel 718 superalloy

Abstract: The Laves phase in the as-built Inconel 718 (IN718) superalloy is known as undesirable phase, which limits the industrial applications of the manufactured parts. Post-processing in the form of the homogenization heat treatment is known as an effective method to eliminate the deleterious Laves phase, where understanding its dissolution kinetics is crucial for optimization of the heat treatment schedule. Accordingly, the IN718 nickel-based superalloy manufactured by the laser powder bed fusion (LPBF), also known as selective laser melting (SLM), was homogenized at temperatures from 950 to 1150 °C for 30 to 120 s, and the Laves phase dissolution was studied by microstructural analysis, its kinetics was modeled by Johnson-Mehl-Avrami-Kolmogorov (JMAK) analysis, and the model was validated by the second Fick's law. The activation energy for Laves phase dissolution was determined as ∼160 kJ/mol with an Avrami exponent of ∼1, which was attributed to the high dislocation density and fine microstructure of the LPBF material, and accordingly, the lattice and grain boundary diffusion of Nb in Ni were characterized as the underlying atomistic mechanisms during the dissolution of the Laves phase. These findings are based on the underlying atomistic mechanisms, which can shed light on the principles of dissolution kinetics of Laves phase in IN718 for additive manufactured parts. Moreover, the conducted comparison among LPBF, directed energy deposition (DED), and conventional casting indicated that the fabricating method and the initial segregation play key roles. In other words, due to its lower segregation degree, LPBF has faster Laves phase dissolution kinetics in comparison with other fabrication methods.

Ultrasonic-Induced Grain Refinement in Laser Cladding Nickel-Based Superalloy Reinforced by WC Particles

Abstract: Laser cladding was used to prepare three composite coatings, i.e., Inconel 718 nickel-based superalloy (IN718), IN718-50 wt.% WC created by adding tungsten carbide (WC) particles and IN718-50 wt.% WC assisted by ultrasonic vibration. The phase composition, microstructure evolution, microhardness, residual stress and tribological properties of the three coatings were studied. The addition of WC enhances hardness and improves tribological properties, but also causes aggregation and considerable formation of carbides associated with rough structure. Ultrasonic vibration greatly refines the solidification microstructure, as it can break the growing dendrites, reduce the aggregation of reinforced particles and refine solidified structure. The average microhardness of the latter two composite coatings was increased by 36.37% and 57.15%, respectively, compared with the first IN718 coating, and the last composite coating (ultrasonic assistance) had the lowest COF (0.494). The WC particles and refined carbides converted the wear mechanism from adhesive wear to abrasive wear. In addition, the resultant stress on the surface of the composite coating roughly doubled after adding 50 wt.% WC, and only increased by 49.53% with ultrasonic treatment. The simulation results indicate that acoustic cavitation mainly occurs in the middle and bottom of the molten pool and proper frequency ultrasonic is conducive to the generation of the cavitation effect.

A study on developing process-structure–property relationship with molten pool thermal history during laser surface remelting of Inconel 718

Abstract: In the area of laser material processing, laser surface remelting has been found to be an effective method of improving surface properties such as hardness, wear, and corrosion resistance. However, the scale of improvement depends on the evolving microstructure and phases, which depend on the cooling rates. Therefore, in the present study, laser surface remelting of Inconel 718 was carried out and a process-structure–property relationship with respect to the cooling rates has been developed. During the laser surface remelting process, the molten pool thermal history i.e. cooling rate, molten pool lifetime, and solidification shelf time is monitored and estimated using an IR pyrometer. The evolution of microstructure is later correlated with these parameters. With an increase in scan speed, the cooling rate is found to increase resulting in transformation of microstructure from equiaxed grains to columnar epitaxial growth. Based on the results obtained, a process map is proposed to establish a particular type of microstructure with respect to the cooling rate. Further, the effect of cooling rate and microstructure on the surface hardness and specific wear rate has also been investigated. Both surface hardness and specific wear rate got reduced with decreasing cooling rate at a slower scan speed due to grain coarsening and an increase in elemental segregation or Laves phase formation.

Influence of Different Build Orientations and Heat Treatments on the Creep Properties of Inconel 718 Produced by PBF-LB

Abstract: Inconel 718 is a nickel-based superalloy with excellent creep properties and good tensile and fatigue strength. In the field of additive manufacturing, it is a versatile and widely used alloy due to its good processability in the powder bed fusion with laser beam (PBF-LB) process. The microstructure and mechanical properties of the alloy produced by PBF-LB have already been studied in detail. However, there are fewer studies on the creep resistance of additively manufactured Inconel 718, especially when the focus is on the build direction dependence and post-treatment by hot isostatic pressing (HIP). Creep resistance is a crucial mechanical property for high-temperature applications. In this study, the creep behavior of additively manufactured Inconel 718 was investigated in different build orientations and after two different heat treatments. The two heat treatment conditions are, first, solution annealing at 980 °C followed by aging and, second, HIP with rapid cooling followed by aging. The creep tests were performed at 760 °C and at four different stress levels between 130 MPa and 250 MPa. A slight influence of the build direction on the creep properties was detected, but a more significant influence was shown for the different heat treatments. The specimens after HIP heat treatment show much better creep resistance than the specimens subjected to solution annealing at 980 °C with subsequent aging.

A Comprehensive Review on the Conventional and Non-Conventional Machining and Tool-Wear Mechanisms of INCONEL®

Abstract: Nickel-based superalloys, namely INCONEL® variants, have had an increase in applications throughout various industries like aeronautics, automotive and energy power plants. These superalloys can withstand high-temperature applications without suffering from creep, making them extremely appealing and suitable for manufactured goods such as jet engines or steam turbines. Nevertheless, INCONEL® alloys are considered difficult-to-cut materials, not only due to their superior material properties but also because of their poor thermal conductivity (k) and severe work hardening, which may lead to premature tool wear (TW) and poor final product finishing. In this regard, it is of paramount importance to optimise the machining parameters, to strengthen the process performance outcomes concerning the quality and cost of the product. The present review aims to systematically summarize and analyse the progress taken within the field of INCONEL® machining sensitively over the past five years, with some exceptions, and present the most recent solutions found in the industry, as well as the prospects from researchers. To accomplish this article, ScienceDirect, Springer, Taylor & Francis, Wiley and ASME have been used as sources of information as a result of great fidelity knowledge. Books from Woodhead Publishing Series, CRC Press and Academic Press have been also used. The main keywords used in searching information were: “Nickel-based superalloys”, “INCONEL® 718”, “INCONEL® 625” “INCONEL® Machining processes” and “Tool-wear mechanisms”. The combined use of these keywords was crucial to filter the huge information currently available about the evolution of INCONEL® machining technologies. As a main contribution to this work, three SWOT analyses are provided on information that is dispersed in several articles. It was found that significant progress in the traditional cutting tool technologies has been made, nonetheless, the machining of INCONEL® 718 and 625 is still considered a great challenge due to the intrinsic characteristics of those Ni-based-superalloys, whose machining promotes high-wear to the tools and coatings used.