Papers by Keyword: Nickel-Based Alloy

Abstract: In the past few decades Aluminium alloys have been extensively used in most of the structural applications, where there is a need to reduce weight and substantially providing structural strength and stability to the assembly. Aluminium alloys or Titanium alloys are the best possible options for the design engineers to select over alloy steel for structural applications when mass reduction is an important factor, However Aluminium alloys wins the race over Titanium alloys when cost is an important criteria for selection of materials. Aluminium alloys are chosen as an alternative next to titanium alloys when it comes to high strength to weight ratio. Titanium alloys particularly Ti6Al4V is selected for applications where the component is loaded with high temperature. Therefore engineers have to evaluate the loading conditions and its environment based on the properties of alloys for selection of Aluminium alloys over other alloys for structural applications. Material selection for the structural applications in various industries such as aerospace, automotive, Industrial and construction sector are based on its function, which depends on the factors like the loading conditions, environment, and functional requirements. The main strength requirements for structural applications are its mechanical properties namely Tensile strength either compressive or tensile load, The present review is to study and understand the characteristics of Aluminium alloys and ways to enhance the mechanical properties of Aluminium alloys.

Abstract: The addition effect of Mn alloying element on the oxide growth behavior of 800H nickel-based alloy has been study in this paper. The alloy was experienced a cyclic oxidation at 900 °C. The cyclic oxidation test was carried out at oxidizing temperature for one hour followed by cooling at about 200 °C for 20 minutes for each cycle. The test samples were exposed to the cyclic condition up to 150 cycles. The oxidized samples of selected cycles were characterized in term of oxidation kinetic, phase analysis using x-ray diffraction (XRD) spectrometer and oxide scale morphology in plan and cross-sectional view by using scanning electron microscope (SEM) equipped with energy dispersive x-ray (EDX) spectrometer. As a results, the oxidation kinetic exhibited a weight gain pattern as the exposure cycle increase. Several protective oxide phases which are Cr₂O₃ and MnCr₂O₄ oxides were formed. In addition, continuous oxides scale was formed on the sample surface with evidence of Cr-Mn and Cr-rich oxide as detected by EDX analysis.

Abstract: The study on solution treated Fe-40Ni-24Cr Ni-based alloy on the isothermal oxidation has been investigated. The solution treatment process has been done at two temperatures, which are 1100°C and 1200°C. The alloys were soaking for 3 hours, followed by rapid cooling using water cooled. The solution treated Fe-40Ni-24Cr Ni-based alloy were experienced an isothermal oxidation test at 700°C for 500 hours exposure time. The effect of Nb alloying element on the oxide growth behavior has been characterized in termed of plan and cross sectional view using scanning electron microscope with energy dispersive x-ray spectrometer. As a results, good protective oxide scale has formed on the fine grain solution treated sample with homogeneous and dense oxide structure. On the other hand, coarse grain solution treated sample demonstrated an oxide exfoliation after 500 hours exposure around the overgrown Nb-rich oxide precipitate area, hence indicating poor oxidation protection.

Abstract: Nickel-based composite coatings reinforced by spherical tungsten carbide were deposited on 42CrMo alloy steel using plasma transfer arc welding (PTAW) process. Their electrochemical corrosion properties in NaCl solution under atmospheric and high pressure were studied by polarization curve, electrochemical impedance spectroscopy. The corrosion and erosion resistance of the coatings were also investigated by salt spray corrosion and erosion corrosion tests. The results show that the self-corrosion potential of the composite coatings increased with the increase of tungsten carbide content, and the Cr element in Ni60 sample formed a stable and compact passivation film. Compared with corrosion at atmospheric pressure, the adsorption and penetration of Cl^- on the coating surface enhanced due to the increase of Cl^- activity under pressure, thereby to weaken the corrosion resistance. The Samples that passivated in salt spray environment, cannot completely hinder the corrosion of the coating, just only to slow down the corrosion. This study can provide theoretical basis for deep-sea oil drilling and production engineering equipment.

Abstract: The present study was conducted by transmission electron microscopy (TEM) in order to investigate the structure of multicomponent nickel-based alloy obtained by directional solidification and change in its phase composition at high-temperature annealing. All states of the alloy possessed monocrystalline structure with [001] orientation. The alloy under study contained other elements apart from Ni, such as: Al, Co, and also Mo, Cr, W, Ta, Re, and Ru. The alloy was investigated in three states after annealing for: 1) 118 h; 2) 372 h; 3) 1274 h at 1000°С. The basic phases that form the alloy were γ and γ′. In the state after annealing for 118 h Al₆(Re,Ru) phase was observed in an insignificant amount. After longer high temperature annealing new phases occurred, such as σ-phase and δ-phase, Laves phase. The structures occurring during annealing can be classified into four types: 1) quasi-cuboids, 2) anisotropic stripe structures, 3) anisotropic structures of striped type with σ-phase separation, 4) structureless zones with large two-phase areas.

Abstract: Environmentally assisted cracking (EAC) of nickel-based alloys is one of the most significant potential safety hazards in the primary circuit of nuclear power plants. To understand the influence of randomness on micro-mechanical state at tip of EAC, Latin hypercube sampling method is applied to analyze the uncertainty of stress-strain in the oxide film at the EAC tip considering the uncertainties of load and material properties of base metal and oxide film. Meanwhile, to improve the efficiency of numerical analysis, MATLAB is employed in the secondary development for ABAQUS. With the help of finite element numerical simulation and Latin hypercube sampling method, the uncertainty of mechanical properties at tip of EAC in one-inch compact tension specimen is simulated and analyzed in this study. The results show that the randomness of material properties and load markedly affect the uncertainty of micro-mechanical state. Among the variables, The randomness of load has the greatest influence on uncertainty of strain, and Poisson`s ratio of oxide film is the smallest effect.

Abstract: In this study, corrosion behavior of Incoloy 800 was studied in supercritical water containing sewage sludge and oxygen at various temperature from subcritical to supercritical environment. Surface and cross-section morphologies of the oxide films on Incoloy 800 was observed by scanning electron microscope. Corrosion will be obviously accelerated by increasing temperature. And the addition of oxygen in corrosion medium will cause the formation of various inorganic salts, forming a salt deposit layer on sample surface.

Abstract: Corrosion behavior of Incoloy 825 was studied in high temperature vapor with high concentration of NaCl. After 80 h exposure, a bi-layer structure was formed on sample surface after exposure. The outer layer is consisted of loose and large-grain oxides, and the inner layer is composed of fine-grain oxide. The whole layer was identified to be CrOOH/Fe₃O₄/Cr₂O₃/Incoloy 825 from outer to inner.

Abstract: A process for grinding deep profiled slots in a nickel-based alloy with electroplated cubic boron nitride (CBN) wheels and straight oil is presented. These slots were prepared by this process for further grinding with electroplated CBN quills to generate the final fir-tree slots in gas turbine disks. Fir-tree slots are usually machined using broaching. The application of broaching, however, is limited in the case of nickel-based powder metal alloys due to short life of broaching tools and the effect on machined surface integrity. Grinding tests were first conducted on rectangular blocks to grind slots without inclinations at a fixed wheel speed v_s = 60 m/s to identify the combinations of depths of cut, workspeed, and up/down grinding satisfying the requirements of ground surface quality and material removal rate. Inclined slots were then ground with the identified condition on a block representing a segment of an actual turbine disk to validate the condition. The wheel life was finally tested by grinding all the slots on the actual disk. Grinding power was measured, and the ground surfaces were inspected for any sign of burning. Preset target material removal rate and wheel life were obtained. It was found that electroplated CBN wheels are capable of grinding deep profiled slots on the difficult-to-cut nickel-based alloy.

Abstract: The wetting and spreading behaviors of pure nickel and nickel based alloys on sintered ZrB₂-SiC ceramics and their interfacial microstructures were investigated in this presentation. The nickel-based alloys were mainly the commercial nickel-molybdenum-chromium products. The wetting and spreading properties were observed by a real-time thermal optical measurement system under flowing argon-5%hydrogen atmosphere. As temperature increased, the pure nickel cylinder sample on ZrB₂-SiC substrate had few changes before 1228°C except for the thermal expansion in size. After that, liquid phase formed and spread gradually on the ceramic substrate. The contact angle was about 15^o after holding 15min at 1600°C. Therefore, pure nickel could contact sintered ZrB₂-SiC ceramics well. Meanwhile, the introduction of molybdenum and/or chromium in the pure nickel was beneficial for the wetting of nickel on sintered ZrB₂-SiC ceramics. The contact angles of Ni-28Mo and Ni-16Mo-23Cr alloys on sintered ZrB₂-SiC ceramics after 1600°C/15min were 13^o and 2^o, respectively. In addition, the temperatures of the liquid drop formed rose obviously in contrast to the pure nickel. The SEM images indicated that the interfacial microstructures of Ni-based alloys on sintered ZrB₂-SiC ceramic substrates were uniform and the dissolved boundaries showed that they had a good bonding. However, some cracks were found in the Ni/ZrB₂-SiC system for their high thermal mismatch. On the other hand, the Ni-Mo (-Cr)/ZrB₂-SiC interface had few defections and evident elemental diffusion between the ceramic substrates and the alloys were found at the interface.