Nimonic 80A Alloy Research Articles

Micro- and nano-mechanical approach to fracture toughness determination of borided layer produced on Nimonic 80A-alloy

Borided layer produced on Nimonic 80A-alloy by plasma paste boriding ensure the high hardness and wear resistance. However, the high hardness and Young’s modulus of this layer contribute to its susceptibility to cracking. The fracture toughness was investigated using two approaches: micro-mechanical (crack-length-based method) and nano-mechanical (crack-energy-based method). In the case of the crack-length-based method, there was a strong correlation between the length of cracks produced from the corners of Vickers indent and the applied load. In order to characterize the susceptibility to cracking without loading, the KC0 coefficient was determined from the plot representing KC vs. indentation load. This parameter ranged from 1.5324 MPa·m1/2 to 3.6880 MPa·m1/2, depending on the applied model (Palmqvist, Casellas, Shetty, Niihara, Lankford and Laugier). The use of the crack-energy-based method resulted in a higher (even three times) fracture toughness compared to the crack-length-based method. It was found, that the KC values determined by Berkovich nanoindentation represents the absolute fracture toughness independent of the applied load and not related to crack formation.

Influence of Laser Beam Power on the Temperature Distribution and Dimensions of the Molten-Pool Formed during Laser Boriding of Nimonic 80A-Alloy

Laser boriding is a surface treatment that involves the simultaneous re-melting and mixing of the alloying material, containing amorphous boron blended with diluted polyvinyl alcohol, with the substrate material (Nimonic 80A-alloy). As a result of high cooling rates, the boride layer is formed from a solidifying molten pool. The thickness of the produced layer depends on the laser treatment parameters, e.g., power of the laser beam, scanning rate, and laser beam radius. These parameters influence the temperature distribution on the cross-section of laser tracks and, thus, directly determine the size of the molten pool, from which the boride layer is formed after crystallization. In the present study, laser borided layers were produced on Nimonic 80A alloy using a CO2 molecular laser. Differences in the laser beam power used resulted in the formation of layers of different thicknesses, which resulted directly from the differences in the temperature distribution in the treated material. The amount of boron in the molten pool directly influenced the obtained hardness of the laser borided layer. It was found that the lower laser beam power had an advantageous effect on the hardness due to the higher percentage of nickel borides and chromium borides in the layer. The reasons for this situation are discussed in detail.

The importance of plasma paste boriding parameters for thickness, nanomechanical properties, residual stress distribution and fracture toughness of layers produced on Nimonic 80A-alloy

Borided layers of different thickness were produced on Nimonic 80A-alloy using plasma paste boriding method. The process was carried out at the temperature of 750 °C, 800 °C and 850 °C for 3 h and 6 h. All produced layers consisted of a fine-grained mixture of nickel borides and chromium borides. Higher boriding temperature and time resulted in the obtaining of boron-rich CrB phase in the microstructure of the borided layer. Simultaneously, this layer was characterized by higher hardness and Young’s modulus. Compressive residual stresses were generated in all produced layers. However, the most advantage course of the curve is characteristic of the borided layer produced at the highest temperature and time. The increase in layer thickness was accompanied by a decrease in the crack’s length (from 33.8 to 7.7 µm), as well as an increase in the fracture toughness (from 0.4439 to 2.4087 MPa·m1/2).

Very high cycle fretting fatigue of Nimonic 80A modified by laser cladding with Stellite X-40 and In625/20 % WC

Nimonic 80A alloy is widely used in rotor blades, guide vane supports and other aeroengine components. It is exposed to harsh fretting wear and high temperature loads, which reduces the fatigue resistance of the components. Laser cladding (LC) technology is utilized to improve structural integrity and fatigue resistance. The aim of the research is to assess the resistance of Nimonic 80A in the very high cycle fretting fatigue (VHCFF) after cladding with Stellite X-40 and In625 + 20 wt% WC. The wear morphology and fracture mechanism of the specimens were studied using scanning electron microscope (SEM) and confocal laser scanning microscope (CLSM). The results show that the crack initiation sites are mainly classified into three types, namely surface initiation, interior initiation, and LC interface initiation. The fretting wear introduces compressive residual stress along the wear depth, as well as the bulk stress, residual stress, and cladding defects all play dominant roles in crack initiation. Especially up to 108 cycles, the glaze oxide layer (GOL) helps to reduce friction coefficient and make the compaction of wear debris easier, inhibiting the crack nucleation. The different distribution of residual stress in on the LC layer and the stronger wear resistance of WC particles lead to the higher fatigue strength and life of the specimen with In625 + 20 wt% WC cladding material compared with the Stellite X-40 ones.

Experimental examination of the machining characteristics of Nimonic 80-A alloy on wire EDM

Nimonic 80-A alloys are very hard alloys with high-temperature strength having an extensive application in the aerospace industry. Wire Electric Discharge Machining (WEDM) is one of the finest non -conventional machining processes, which due to the material removal taking place using spark erosion with Wire EDM, makes it very easy to machine hard alloys and composites. The accuracy of machining them makes it one of the most advanced non-traditional processes. Kerf width is an important output response during machining on WEDM. The experimental investigation is done to find the optimum machining parameters to minimize the kerf width. The experimental investigation was done using the Taguchi analysis considering input factors peak current, gap voltage, and pulse-on time at three levels for machining on WEDM. Taguchi L27 orthogonal array was applied to generate the required experiments to be performed on WEDM. The output response data kerf width obtained is analyzed using signal-to-noise (S/N) ratio values generated by the Taguchi design methodology. The three main input parameters like peak current (20-80A), gap voltage (30–60 V), and pulse-on time (20–70 μs) are considered within this range. The single response optimization is done of the experimental kerf width data obtained for 27 different settings of input parameters of WEDM. The influence of each of the variables on kerf width is interpreted using the S/N ratio graphs, finding the most appropriate settings to minimize the kerf width. The results were obtained with a specific range of parameters that can be analyzed further with other optimization models, to get a wider range of optimum parameter values. The research on optimizing the output response kerf width for Nimonic 80-A alloy during machining on WEDM has not been reported much in the literature. This new optimized machining data would provide better scope to machine Nimonic 80- A alloy for minimizing the kerf width.

Impact of hybrid cooling approach on milling and surface morphological characteristics of Nimonic 80A alloy

Poor surface traits, short insert life, high manufacturing costs, and low productivity are associated with the machining of nickel alloys. Cutting fluids have well-known positive and negative effects on machinability performance. As a result, the machining industry has developed green cutting environments such as vegetable oil assisted minimum quantity lubrication (MQL) and cryogenic cooling. Despite the fact that MQL and cryogenic approaches can replace mineral oil-based flooding, their lack of lubrication and cooling properties at high speeds have prompted a search for a new hybrid approach (CO2 + MQL) that provides adequate cooling/lubrication (C/L). Moreover, as of now, no information concerning the effects of hybrid cooling on milling of Nimonic-80A is existing. To test the viability, the machining of Nimonic-80A under hybrid C/L was compared to other cutting environments (MQL and cryogenic). As crucial machinability factors, temperature, power consumption, surface and subsurface characteristics were thoroughly examined. Hybrid condition curtailed the burr formation, which paves the way for a reduction in specific cutting energy (SCE). The experimental results indicate that the hybrid condition considerably decreases the temperature and SCE by 34–53% and 17–19% in comparison with the MQL condition. Peak widening and intensity reduction were seen in the XRD examination, but no phase transition was found. Smaller grain size shows the superiority of hybrid environment.

Growth Kinetics and Some Mechanical Properties of Plasma Paste Borided Layers Produced on Nimonic 80A-Alloy

Plasma paste boriding was employed in order to produce the boride layers on Nimonic 80A-alloy. The process was carried out at temperatures of 1023 K, 1073 K and 1123 K for 3, 4 and 6 h in a gas mixture of 50% H2-50% Ar. Borax paste was used as a boron source. The microstructure of the produced surface layers consisted of the mixture of nickel borides and chromium borides. The effect of processing temperature and duration on the thickness of the borided layers was observed. The theoretical thicknesses of the borided layers were estimated using an integral diffusion model. A good correlation was obtained between the theoretical (modeled) and experimental depths of the plasma paste borided layers. The boride layers were characterized by a high hardness ranging from 1160 HV to 2132 HV. The multiphase character of the produced layers resulted in differences in hardness. A significant improvement of the wear resistance of the plasma paste borided Nimonic 80A-alloy was observed in comparison with the non-borided alloy.

Low-temperature aluminizing influence on degradation of nimonic 80A surface: Microstructure, wear and high temperature oxidation behaviors

Nimonic 80A alloy has been subjected to aluminizing process to improve its high temperature oxidation and wear properties. Pack aluminizing process was carried out for 3 and 5 h at 650 and 700 °C temperatures without using a protective atmosphere. Aluminising treatment was carried out using metallic aluminium, ammonium chloride (NH4Cl) and alumina as a filler. The morphology and structure of aluminide layers was analysed by SEM-EDS. It was observed that there was a super bonding between matrix and coating layers which are smooth, dense and porosity free. Dominant phases of Ni2Al3 and Al80Cr20 were detected by XRD analysis. Layer thickness was measured from the surface to the matrix and changed from 20 to 70 μm which was increased with increasing process duration and temperature. The matrix hardness is 400 HVN while the hardness of coating layer raised to 1025 HVN with the process time and temperature. Wear losses decreased with the increase in coating temperature and time in both high temperature and room temperature tests. After isothermal oxidation tests at 1000 °C up to 75 h, all aluminized samples consist of alumina scale while Nimonic 80A consist of Cr2O3 and TiO2 mixed oxides with high thickness. The increased aluminizing temperature and time provide better protection against high temperature oxidation.

Optimization and neural modelling of infiltration rate in ultrasonic machining

Ultrasonic machining is a processing method typically practiced for processing the highly brittle/hard materials. The proposed research work is attempted at exploring the influence of varying input conditions namely; cobalt %, power rating, thickness of work, different tools, tool geometry, and abrasive size on the infiltration rate in ultrasonic drilling of WC–Co composite through neural modelling. The design of experiments methodology has been practiced for scheming out the experiments. The significant process variables have been acknowledged using variance analysis test which has revealed the abrasive size, power rating, and tool profile as the most influential factors for the infiltration rate. An artificial neural network (ANN) model is suggested to analyze the infiltration rate in USM with striking parameters. Multiple layer feed frontward neural architecture is restrained through error-back propagation-based training algorithm. Predicted results show the effectiveness of the proposed neural structure with maximum error of 6%. The optimized parametric combination for infiltration rate has been revealed as; cobalt- 6%, work thickness- 3 mm, tool- hollow, tool material- nimonic-80A alloy, abrasive size- 200, and power rating- 80%. Microstructure analysis revealed that good edge quality with no appearance of cracks or burr/chipping on the edge of the drilled holes which further ensured the quality level of hole drilling through attempted work.

Experimental investigation of machining nimonic-80A alloy on wire EDM using response surface methodology

This paper aims to optimize the wire electric discharge machining (WEDM) parameters using multi response surface methodology. Experiments were performed on Nimonic 80A alloy to improve the response variables, namely material removal rate (MRR) and Kerf width (Kw). SEM analysis was carried out on the different samples obtained using different levels of input input parameters, namely, peak current, gap voltage, duty cycle and wire speed to evaluate the quality of machined surface. The influence of these parameters on MRR and Kw were determined using ANOVA. The analysis results revealed that the peak current is the main factor affecting MRR and Kw. The optimized WEDM parameters obtained using multi response function of RSM technique for machining of Nimonic 80A alloy are peak current (57A), gap voltage (90 V), duty cycle (75 µs), and wire speed (7 mm/min) of wire electrode. The characterization results show that high discharge energy results in deep craters with micro craters at low energy levels on the machined surface of the specimen. The results obtained using the proposed methodology would provide sufficient data for enhancing the machining of Nimonic 80A alloy on WEDM.

Performance analysis of coated carbide tool in turning of Nimonic 80A superalloy under different cutting environments

Nimonic 80A is a difficult-to-machine nickel-based superalloy thanks to its superior tensile strength in high temperatures and oxidation resistance. However, cutting fluids applied to improve machinability performance during the processing of such materials increase tool life, while at the same time increasing machining costs and causing health and environmental problems. Thus, the present research has been focused on cutting tool life and wear characteristics and analysis of machined surface in turning of Nimonic 80A superalloy under different cutting environments namely dry, air-cooling and oil-spraying method. The performance of the coated tool has been characterized by using optical microscope, SEM and EDS analysis. The results of the tool life and microscopic analysis showed that the oil-spraying method has longer tool life than dry and air-cooling method in turning of Nimonic 80A alloy. Moreover, the volume of material removed has been modeled by response surface method for predicting tool performance under various machining conditions. Lastly, the microstructural and microhardness variations of the machined surface have been evaluated when the cutting tool reaching the wear criterion. The best performance in terms of tool life and surface integrity was obtained at cutting speed of 60 m/min in oil-spraying environment.

Investigation of tensile Johnson-Cook model parameters for Nimonic 80A superalloy

Developing high temperature technology increases the need for high temperature resistant materials. Nimonic 80A alloy is generally preferred due to its high creep resistance, oxidation resistance and high resistance to high temperature corrosion. The study determines the tensile constitutive equation (JC parameters) of Nimonic 80 A superalloys. Johnson Cook (JC) model is preferred amongst the various material constitutive equations (Zerille Armstrong, Bordner Partom, JC model). Three different kinds of tensile experiment were performed to identify the model parameters. These are quasi-static tensile experiments applied at room temperatures. These experiments were carried out at 0.001, 0.01 and 0.1 s−1 strain rates. Therefore, the reference strain rate for all experiments was selected to be 10−3. As a second test, tensile experiments were conducted at room temperature at high strain rates (102–103 s−1) using the Split Hopkinson pressure bar (SHPB). Lastly, tensile experiments were conducted at high temperatures (300–900 °C) at 0.001 s−1. It was observed whether all tests are compatible with each other or not, and so five Johnson-Cook (JC) parameters of Nimonic 80 A alloy were identified via the data found from the experiments. After determination of parameters, tensile test simulations by finite element method (FEM) were performed in ANSYS Workbench. As a result, the accuracy of the JC parameters is verified since there is a deviation of %2.84 between the experimental and the simulation results.

Effects of aggregation kinetics on nanoscale colloidal solution inside a rotating channel

The objective of the present investigation is to reveal the effects of aggregation kinetics on the nanofluid flow between two revolving plates. Additionally, we have presumed that the upper surface of the revolving structure is permeable while the lower one is blessed to move with variable speed. Here we have introduced Nimonic 80A alloy nanoparticles with water as a base liquid. Aggregation kinetics at molecular level has been introduced mathematically to model our work and to explore how aggregation features affect the thermal integrity of the system. Similarity technique guided us to avail non-dimensional form of leading equations. RK-4 method along with shooting technique aids us to solve nonlinear ODEs. Several features of aggregation parameters on velocity and temperature profile have been explored through graphs and tables. Results extract that effective thermal conductivity of aggregated composite increases for nanoparticle volume fraction. Heat transport drops off for radius of gyration factor at lower segment but rises at upper regime.

Influence of niobium and molybdenum addition on microstructure and wear behavior of laser-borided layers produced on Nimonic 80A-alloy

Abstract Laser alloying was used for production of thick layers on surface of Nimonic 80A-alloy. For laser surface modification, three types of pre-coated pastes were applied: with amorphous boron, with amorphous boron and molybdenum as well as with amorphous boron and niobium. The microstructure, hardness and wear resistance of produced layers were studied in details. The presence of different types of borides in re-melted zone depended on the paste composition and caused an increase in hardness up to about HV 1000. The wear resistance was evaluated by calculation of mass wear intensity factor Imw and relative mass loss of specimen and counter-specimen. The wear behavior of the tested frictional pairs was determined by 3D interference microscopy, scanning electron microscopy equipped with EDS microanalyzer. The significant increase in abrasive wear resistance was observed in comparison to untreated Nimonic 80A-alloy. The lowest mass loss intensity factor was characteristic of laser-alloyed Nimonic 80A-alloy with boron and niobium (Imw=1.234 mg/(cm2·h)). Laser alloyed-layers indicated abrasive wear mechanism with clearly visible grooves. Laser alloying with boron and niobium resulted in the additional oxidative wear mechanism. In this case, EDS patterns revealed presence of oxygen on the worn surface of specimen.

On Surface Topography and Microstructure in Cavitation Erosion Tests of Alloy 80 A

From practical and economic reasons for the design of components for Diesel engines, the selection of materials and/or heat treatments is essential to provide a high cavitation erosion resistance. This paper studies cavitation behavior of the Nimonic 80A alloy designed for execution of Diesel engine exhaust valves. The cavitation tests where done on an ASTM G32 -2010 compliant vibrating device with piezoceramic crystals.The metalographic examinations performed with optical microscope and electronic scanning microscopy revealed the microstructural changes occurring in the region of the cavitation affected material and the path of the crack propagation

Characterization of laser-borided Nimonic 80A-alloy

Nimonic 80A-alloy belongs to Nickel-based superalloys. Many of them are used in variety branches of industry due to high strength and resistance in aggressive conditions. Moreover, its mechanical properties are kept in high temperature. However, these materials should be coated by appropriate wear protection, under conditions of considerable mechanical wear. Unfortunately, the production of thick borided layer in diffusion boriding required high temperature and long duration of this processes. Therefore, in this study instead conventional diffusion process laser boriding was applied in order to produce boride layer on Nimonic 80A-alloy substrate. Laser alloying is the high-tech process which allows to modify the chemical composition of the surface. Laser boriding was arranged as a single tracks, therefore it was possible to evaluate the influence of laser treatment parameters on thickness and hardness of produced layers. The laser beam power P, laser scanning speed vl and laser beam diameter dl were the variable parameters used during laser alloying.

The effect of laser treatment parameters on temperature distribution and thickness of laser-alloyed layers produced on Nimonic 80A-alloy

Purpose: The aim of this paper was to determine the influence of laser treatment parameters on temperature distribution and thickness of laser-alloyed layers produced on Nimonic 80A-alloy. Design/methodology/approach: In this paper laser alloying was used in order to produce layers on Nimonic 80A-alloy surface. The three types of the alloying materials were applied: B, B+Nb and B+Mo. Microstructure observations were carried out using an optical microscope. The hardness measurements were performed using a Vickers method under a load of 0.981 N. For evaluation of temperature distribution the equations developed by Ashby and Esterling were used. Findings: The produced layers consisted of re-melted zone only and were characterized by high hardness (up to 1431 HV0.1). The increase in laser beam power caused an increase in thickness and decrease in hardness of re-melted zones. The temperature distribution was strongly dependent on laser treatment parameters and physical properties of alloying material. The higher laser beam power, used during laser alloying with boron, caused an increase in layer thickness and temperature on the treated surface. The addition of Mo or Nb for alloying paste caused changes in melting conditions. Research limitations/implications: The obtained results confirmed that laser beam power used for laser alloying influenced the thickness and hardness of the produced layers. Moreover, the role of type of alloying material and its thermal properties on melting condition was confirmed. Practical implications: Laser alloying is the promising method which can be used in order to form very thick and hard layers on the surface of Ni-base alloys. The obtained microstructure, thickness and properties strongly dependent on laser processing parameters such as laser beam diameter, laser beam power, scanning rate as well as on the type of alloying material and its thickness, or type of substrate material. Originality/value: In this paper the influence of alloying material on temperature distribution, thickness and hardness of the laser-alloyed layers was in details analyzed.

Natural convective heat transfer analysis of MHD unsteady Carreau nanofluid over a cone packed with alloy nanoparticles

The present numerical simulations are carried out to investigate the effect of viscous dissipation, temperature dependent viscosity and heat source/sink on magnetohydrodynamics (MHD) unsteady Carreaue nanofluid over a cone filled with different alloy nanoparticles. We considered two different types of alloy nanoparticle namely nickel chromium iron alloy (Nimonic 80A) and titanium aluminum vanadium alloy (Ti%6Al%4V). The governing equations of the flow are solved using the Runge-Kutta and Newton's method. The present numerical results are compared with the previous study and found agreement with the uncertainty of ±2.5%. Effects of various non-dimensional parameters such as Eckert number, power index parameter, volume fraction, heat source/sink parameter, viscous variation parameter and semi-vertical angle of the cone on the momentum and thermal boundary layer including the friction factor coefficients and local Nusselt number are presented and analyzed for two different alloy considered in the present study. It is found that the viscous variation parameter enables to enhance the heat transfer rate. The Ti%6Al%4V alloy has higher friction factor coefficient along the azimuthal direction of the flow while Nimonic 80A alloy boosts up the friction coefficient along the tangential direction. It is worth to mention that the heat transfer rate of Nimonic 80A alloy is higher than that of Ti%6Al%4V alloy. Hence, Nimonic 80A alloy signifies a better thermal performance than the Ti%6Al%4V alloy.

Corrosion Behavior of Hard Boride Layer Produced on Nimonic 80A-Alloy by Gas Boriding

The gas boriding in N2–H2–BCl3 atmosphere was applied in order to produce a wear resistant surface layer on Nimonic 80A-alloy samples. The microstructure, microhardness and corrosion resistance of the boride layer were investigated. The produced layer consisted mainly of the compact boride zone (with average thickness 71 μm), including the mixture of nickel and chromium borides of high hardness (up to 1861 HV). In order to evaluate the corrosion behavior, the two methods of corrosion tests were used: potentiodynamic corrosion test in 5% NaCl solution and immersion corrosion test in a boiling solution of H2O, H2SO4 and Fe2(SO4)3. The results showed that gas boriding could provide the excellent corrosion resistance if the whole surface of a Nimonic 80A-alloy sample was covered by the continuous boride layer. Otherwise, as a consequence of selective boriding, the significant difference in electrochemical potentials caused an accelerated uniform corrosion of the base material.

Nanomechanical properties of gas-borided layer produced on Nimonic 80A-alloy

Abstract Diffusion borided layers, fabricated on Ni-based alloys, were characterized by improved hardness and wear resistance. In this paper, gas boronizing in N 2 –H 2 –BCl 3 atmosphere was proposed to produce the ceramic phases (borides) on Nimonic 80A-alloy. This process was carried out at 920 °C (1193 K) for 2 h. The microstructure was studied in detail using scanning electron microscope and energy-dispersive X-ray microanalysis. The boride layer consisted of a mixture of nickel borides (Ni 3 B, Ni 2 B, Ni 4 B 3 , NiB) and chromium borides (CrB, Cr 2 B). The nanomechanical properties (Young's modulus and hardness) were examined using the nanoindenter with a Berkovich diamond tip. The load-displacement curves and the indentation images were shown for the selected measurements. The identified phases in microstructure were very fine, therefore it was impossible to measure the hardness and Young's modulus of a defined phase. However, the percentage of chromium and nickel borides’ mixtures was calculated based on the measurements of indentation hardness ( H IT ) compared to the previous work. It enabled to calculate Poisson's ratio for a specified indentation. As a consequence, the indentation moduli E IT were determined. The higher values of H IT and E IT were obtained in case of indents, performed in the areas of higher percentage of chromium borides.