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Article
Publication date: 1 September 2006

H. Singh, D. Puri, S. Prakash and M. Srinivas

To characterise the high temperature oxide scales for some plasma sprayed NiCrAlY coated Ni‐ and Fe‐based superalloys.

Abstract

Purpose

To characterise the high temperature oxide scales for some plasma sprayed NiCrAlY coated Ni‐ and Fe‐based superalloys.

Design/methodology/approach

Ni‐22Cr‐10Al‐1Y metallic coatings were deposited on two Ni‐based superalloys; Superni 601 and Superni 718 and one Fe‐based superalloy; Superfer 800H by the shrouded plasma spray process. Oxidation studies were conducted on uncoated as well as plasma spray coated superalloys in air at 900°C under cyclic conditions for 50 cycles. Each cycle consisted of 1 h heating followed by 20 min of cooling in air. The thermogravimetric technique was used to approximate the kinetics of oxidation. X‐ray diffraction, SEM/EDAX and EPMA techniques were used to analyse the oxide scales.

Findings

All of the coated, as well as the uncoated, superalloys followed an alnost‐parabolic rate of oxidation. The NiCrAlY coating was found to be successful in maintaining its continuous contact with the superalloy substrates in all the cases. The oxide scales formed on the exposed NiCrAlY coated superalloys were found to be intact and spallation‐free. The main phases analysed for the coated superalloys were oxides of nickel, chromium and aluminium and spinel of nickel and chromium, which are expected to be useful for developing oxidation resistance at high temperatures.

Practical implications

The coated superalloys showed remarkable cyclic oxidation resistance under simulated laboratory conditions. However, it is suggested that these coated superalloys also should be tested in actual industrial environments of boilers and gas turbines, etc. so as to obtain more practical and reliable oxidation data.

Originality/value

The knowledge of the reaction kinetics and the nature of the surface oxide scales formed during oxidation is important for evaluating the alloys for their use and degradation characteristics in high temperature applications such as steam boilers, furnace equipment, heat exchangers and piping in chemical industry, reformer, baffle plates/tubes in fertilizer plants, jet engines, pump bodies and parts.

Details

Anti-Corrosion Methods and Materials, vol. 53 no. 5
Type: Research Article
ISSN: 0003-5599

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Article
Publication date: 2 August 2021

Modupeola Dada, Patricia Popoola and Ntombi Mathe

This study aims to review the recent advancements in high entropy alloys (HEAs) called high entropy materials, including high entropy superalloys which are current…

Abstract

Purpose

This study aims to review the recent advancements in high entropy alloys (HEAs) called high entropy materials, including high entropy superalloys which are current potential alternatives to nickel superalloys for gas turbine applications. Understandings of the laser surface modification techniques of the HEA are discussed whilst future recommendations and remedies to manufacturing challenges via laser are outlined.

Design/methodology/approach

Materials used for high-pressure gas turbine engine applications must be able to withstand severe environmentally induced degradation, mechanical, thermal loads and general extreme conditions caused by hot corrosive gases, high-temperature oxidation and stress. Over the years, Nickel-based superalloys with elevated temperature rupture and creep resistance, excellent lifetime expectancy and solution strengthening L12 and γ´ precipitate used for turbine engine applications. However, the superalloy’s density, low creep strength, poor thermal conductivity, difficulty in machining and low fatigue resistance demands the innovation of new advanced materials.

Findings

HEAs is one of the most frequently investigated advanced materials, attributed to their configurational complexity and properties reported to exceed conventional materials. Thus, owing to their characteristic feature of the high entropy effect, several other materials have emerged to become potential solutions for several functional and structural applications in the aerospace industry. In a previous study, research contributions show that defects are associated with conventional manufacturing processes of HEAs; therefore, this study investigates new advances in the laser-based manufacturing and surface modification techniques of HEA.

Research limitations/implications

The AlxCoCrCuFeNi HEA system, particularly the Al0.5CoCrCuFeNi HEA has been extensively studied, attributed to its mechanical and physical properties exceeding that of pure metals for aerospace turbine engine applications and the advances in the fabrication and surface modification processes of the alloy was outlined to show the latest developments focusing only on laser-based manufacturing processing due to its many advantages.

Originality/value

It is evident that high entropy materials are a potential innovative alternative to conventional superalloys for turbine engine applications via laser additive manufacturing.

Details

World Journal of Engineering, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 1708-5284

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Article
Publication date: 4 September 2017

S.B. Mishra, Kamlesh Chandra and Satya Prakash

The purpose of this study is to investigate the application of Ni3Al coating for boilers and other power plant equipment, which suffer severe erosion-corrosion problems…

Abstract

Purpose

The purpose of this study is to investigate the application of Ni3Al coating for boilers and other power plant equipment, which suffer severe erosion-corrosion problems resulting in substantial losses. Currently, superalloys are being used to increase the service life of the boilers. Although the superalloys have adequate mechanical strength at elevated temperature, they often lack resistance to erosion-corrosion environments.

Design/methodology/approach

In this paper, the erosion-corrosion performance of plasma-sprayed nickel aluminide (Ni3Al) coating on nickel- and iron-based superalloys have been evaluated by exposing them to the low temperature primary superheater zone of the coal-fired thermal power plant at the temperature zone of 540°C for ten cycles of 100 h duration. The exposed products were analysed along the surface and cross-section using scanning electron microscopy (SEM), X-ray diffraction (XRD) and electron micro probe analysis (EPMA).

Findings

The XRD, SEM and EPMA analyses have shown the formation of mainly NiO, NiAl2O4 and indicated the presence of Ni3Al, Ni and Al2O3. In the boiler environment, Ni3Al coating partially oxidizes and acts as a perfect barrier against erosion-corrosion of superalloys. The partially oxidised Ni3Al coating remains intact even after 1,000 h cycle exposure.

Originality/value

The probable mechanism of attack for the plasma-sprayed Ni3Al coating in the given boiler environment is presented.

Details

Anti-Corrosion Methods and Materials, vol. 64 no. 5
Type: Research Article
ISSN: 0003-5599

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Article
Publication date: 1 April 2005

Harpreet Singh, D. Puri and S. Prakash

Plasma spray coating technologies are capable of depositing a wide range of compositions without significantly heating the substrate. The objective is to characterise…

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Abstract

Purpose

Plasma spray coating technologies are capable of depositing a wide range of compositions without significantly heating the substrate. The objective is to characterise plasma sprayed metallic coatings on a Fe‐based superalloy.

Design/methodology/approach

NiCrAlY, Ni‐20Cr, Ni3Al and Stellite‐6 metallic coatings were deposited on a Fe‐based superalloy (32Ni‐21Cr‐0.3Al‐0.3Ti‐1.5Mn‐1.0Si‐0.1C‐Bal Fe) by the shrouded plasma spray process. The coatings were characterised in relation to coating thickness, porosity, microhardness and microstructure. The high temperature oxidation behaviour of the coatings was investigated in brief. The techniques used in the present investigation include metallography, XRD and SEM/EDAX.

Findings

All the coatings exhibited a lamellar structure with distinctive boundaries along with the presence of some porosity and oxide inclusions. The microhardness of the coatings was observed to vary with the distance from the coating‐substrate interface. The St‐6 coating had the maximum microhardness, whereas the lowest hardness was exhibited by the Ni3Al coating. The phases revealed by XRD of the coatings confirmed the formation of solid solutions, whereas EDAX analysis of the as‐sprayed coatings confirmed the presence of basic elements of the coating powders. So far as high temperature oxidation behaviour is concerned, all of the coatings followed the parabolic rate law and resulted in the formation of protective oxide scales on the substrate superalloy.

Originality/value

The plasma spray process provides the possibility of developing coatings of Ni3Al as well as commercial available NiCrAlY, Ni‐20Cr and St‐6 powders on Fe‐based superalloy Superfer 800H

Details

Anti-Corrosion Methods and Materials, vol. 52 no. 2
Type: Research Article
ISSN: 0003-5599

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Article
Publication date: 17 October 2017

Lanlan Qin, Changjun Chen, Min Zhang, Kai Yan, Guangping Cheng, Hemin Jing and Xiaonan Wang

Laser additive manufacturing (LAM) technology based on powder bed has been used to manufacture complex geometrical components. In this study, IN625 superalloys were…

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Abstract

Purpose

Laser additive manufacturing (LAM) technology based on powder bed has been used to manufacture complex geometrical components. In this study, IN625 superalloys were fabricated by high-power fiber laser without cracks, bounding errors or porosity. Meanwhile, the objectives of this paper are to systemically investigate the microstructures, micro-hardness and the precipitated Laves phase of deposited-IN625 under different annealing temperatures.

Design/methodology/approach

The effects of annealing temperatures on the microstructure, micro-hardness and the precipitated Laves phase were studied by optical microscope (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive spectrometer (EDS), selected area electron diffraction (SAED), backscattered electron (BSE) imaging in the SEM and transmission electron microscopy (TEM), respectively. The thermal stability of the dendritic morphology about IN625 superalloys was investigated through annealing at temperatures range from 1,000°C to 1,200°C.

Findings

It is found that the microstructure of deposited-IN625 was typical dendrite structure. Besides, some Laves phase precipitated in the interdendritic region results in the segregation of niobium and molybdenum. The thermal stability indicate that the morphology of dendrite can be stable up to 1,000°C. With the annealing temperatures increasing from 1,000 to 1,200°C, the Laves phase partially dissolves into the γ-Ni matrix, and the morphology of the remaining Laves phase is changing from irregular shape to rod-like or block-like shape.

Research limitations/implications

The heat treatment used on the IN625 superalloys is helpful for knowing the evolution of microstructures and precipitated phases thermal stability and mechanical properties.

Practical implications

Due to the different kinds of application conditions, the original microstructure of the IN625 superalloys fabricated by LAM may not be ideal. So exploring the influence of annealing treatment on IN625 superalloys can bring theory basis and guidance for actual production.

Originality/value

This study continues valuing the fabrication of IN625 by LAM. It shows the effect of annealing temperatures on the shape, size and distribution of Laves phase and the microstructures of deposited-IN625 superalloys.

Details

Rapid Prototyping Journal, vol. 23 no. 6
Type: Research Article
ISSN: 1355-2546

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Article
Publication date: 16 May 2019

Peter Prakash F., Muthukannan Duraiselvam, Natarajan S. and Kannan Ganesa Balamurugan

This paper aims to investigate the effect of laser surface texturing (LST) on the wear behavior of C-263 nickel-based superalloy and to identify the optimum wear operating…

Abstract

Purpose

This paper aims to investigate the effect of laser surface texturing (LST) on the wear behavior of C-263 nickel-based superalloy and to identify the optimum wear operating condition.

Design/methodology/approach

C-263 nickel-based superalloy was selected as substrate material and pico-second Nd-YAG laser was used to fabricate the waviness groove texture on their surface. Wear experiments were designed based on Box-Bhenken design with three factors of sliding velocity, sliding distance and applied load. Wear experiments were performed using pin on disc tribometer. Morphologies of textures and worn-out surfaces were evaluated by scanning electron microscopy and energy dispersive spectroscopy. Surface topographies and surface roughness of the textures were evaluated by weight light interferometry. The response surface methodology was adopted to identify the optimum wear operating condition and ANOVA to identify the significant factors.

Findings

LST improves the wear resistance of C-263 nickel-based superalloy by appeoximately 82 per cent. Higher wear rate occurs at maximum values of all operating conditions, and applied load affects the coefficient of friction. Applied load significantly affects the wear rate of un-textured specimen. The interaction of sliding velocity and applied load also affects the wear rate of textured specimens. The optimum parameters to get minimum wear rate for un-textured specimens are 1.5 m/s sliding velocity, 725 m sliding distance and 31 N of applied load. For textured specimens, the optimum values are 1.5 m/s sliding distance, 500 m sliding distance and 40 N of the applied load.

Originality/value

Literature on laser texturing on nickel-based superalloy is very scarce. Specifically, the effect of laser texturing on wear behavior of the nickel-based superalloy C-263 alloy is not yet reported.

Details

Industrial Lubrication and Tribology, vol. 71 no. 6
Type: Research Article
ISSN: 0036-8792

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Article
Publication date: 12 February 2018

Saib Cherif and Boumerzoug Zakaria

The Ni-base superalloy INC738LC is a precipitation strengthened alloy and is widely used in hot sections of gas turbine engines owing to its excellent high-temperature…

Abstract

Purpose

The Ni-base superalloy INC738LC is a precipitation strengthened alloy and is widely used in hot sections of gas turbine engines owing to its excellent high-temperature strength and high hot corrosion resistance. The purpose of this study is to determine the appropriate welding current of Ni-base superalloy INC738LC after two passes of applying the tungsten inert gas (TIG) welding technique.

Design/methodology/approach

Ni-base superalloy INC738LC plates were joined by TIG welding technique by varying the welding current (30, 40 and 50 A). Welded specimens were investigated using optical microscopy, tensile tests, Vickers’s micro-hardness tests and X-ray diffraction (XRD). Optical microscopy was used to characterize fusion zone, heat-affected zone and base metal. Tensile test was conducted to characterize weld strength by determining ultimate tensile strength. Scanning electron microscopy was used to investigate the fracture surfaces after tensile tests. Micro-hardness test was conducted to characterize the welded joint. XRD was applied to determine precipitates formed after welding.

Findings

The ultimate tensile strength results show that the optimum weld current out of the three weld currents was found to be 40 A, which is the closest to that of the base metal.

Originality/value

Many researchers have worked to optimize welding parameters such as current and speed from the microstructural observations and mechanical properties of welded joints. The optimum weld current out of the three weld currents was found to be 40 A.

Details

World Journal of Engineering, vol. 15 no. 1
Type: Research Article
ISSN: 1708-5284

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Article
Publication date: 17 August 2010

Liu Junyan, Han Rongdi and Wang Yang

Green machining is becoming increasingly more popular due to concern regarding the safety of the environment and human health. The important implementation of stricter…

Abstract

Purpose

Green machining is becoming increasingly more popular due to concern regarding the safety of the environment and human health. The important implementation of stricter Environmental Protection Agency regulations associated with the use of ample amount of coolants and lubricants has led to this study on a new green machining technology with application of water vapor as coolants and lubricants in cutting Ni‐based superalloys and titanium alloy Ti‐6Al‐4V with uncoated carbide inserts (ISO Type K10). The purpose of this paper is to show that machining technology with application of water vapour could be an economical and environmentally compatible lubrication technique for machining difficult‐cut‐materials.

Design/methodology/approach

In this paper, the effect of water vapor applications in machining difficult‐cut‐materials have been investigated in detail, the cutting force, the chip deformation coefficient, the rake face wear and the width of tool flank land VB have been examined and analyzed, and a new green cutting technology is researched to machining Ni base superalloys and Ti‐6Al‐4V difficult‐cut‐materials.

Findings

The cutting force of machining Ni base superalloys and Ti‐6Al‐4V was affected by direct water vapor application, being lower than dry cutting and wet machining for all machining conditions; the Λh is the smallest with applications of water vapor as coolants and lubricants compared to dry cutting, pure water and oil water emulsion conditions the tool life extended by about six times than dry cutting, about four times than oil water emulsions at low cutting speed (νc<100 m/min), and about two‐four times than dry cutting, about two‐three time than oil water emulsions at higher cutting speed (νc>100 m/min) during machining Ti‐6Al‐4V with application of water vapor direct into the cutting zone.

Originality/value

The green cutting technology which applies water vapor as coolants and lubricants advocates a new method for machining difficult‐cut‐materials (Ni base superalloys and Ti‐6Al‐4V) without any environment pollution and operator health problem because the cutting force and chip deformation coefficient are reduced, the tool life is extended, and the tool flank wear can be decreased with applications of water vapor as coolants and lubricants to alleviate the adhering and diffusion wear compared to wet cutting and dry cutting.

Details

Industrial Lubrication and Tribology, vol. 62 no. 5
Type: Research Article
ISSN: 0036-8792

Keywords

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Article
Publication date: 5 January 2015

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Abstract

Details

Anti-Corrosion Methods and Materials, vol. 62 no. 1
Type: Research Article
ISSN: 0003-5599

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Article
Publication date: 1 July 2020

Chunmei Ma, Songting Yang, Yuheng Zhang, Kaikun Wang and Huadong Fu

Due to the special service environment of superalloys, this paper aims to obtain effects of temperature and Ti addition on high temperature oxidation behavior of Co-Al-W-B alloys.

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Abstract

Purpose

Due to the special service environment of superalloys, this paper aims to obtain effects of temperature and Ti addition on high temperature oxidation behavior of Co-Al-W-B alloys.

Design/methodology/approach

Isothermal oxidation experiment of Co-Al-W-based alloys were carried out at 800°C, 900°C and 1000°C for different times (3, 5, 10, 20, 50 and 100 h) referring to the method of HB5258-2000. Oxidation weight gain curves and oxidation products were detected.

Findings

The results showed that the average oxidation rates of Co-Al-W-B alloy at 800 °C and 900 °C were 0.489 g·m−2·h−1 and 0.888 g·m−2·h−1, respectively, which belonged to an antioxidant grade. However, the average oxidation rate at 1000 °C was 2.068 g m−2·h−1, belonging to the secondary oxidation resistance class. In the alloy with Ti addition, dense Ti oxides film were formed at the early oxidation stage and then gradually diffused later, which can increase the oxidation resistance of the alloys to some extent. By analyzing the oxidation products of Co-Al-W-B alloy, it was found that a dense Al2O3 layer could be formed when the alloy was oxidized at 800°C. The continuous Al2O3 layer would prevent the oxygen from further spreading and make the alloy into the stable oxidation stage. However, only a non-dense Al2O3 layer were observed with 900°C oxidation.

Originality/value

It can provide references for the composition design, preparation process optimization and protective coating selection of the γ′ phase strengthened cobalt-base superalloys.

Details

Anti-Corrosion Methods and Materials, vol. 67 no. 5
Type: Research Article
ISSN: 0003-5599

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