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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.

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.

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.

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

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.

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.

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.

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.

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

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.

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).

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.

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

THE complex annular structures of turbine aero engines are commonly fabricated from a mixture of precision machined forgings, flash welded, cold rolled and sheet metal rings. These rings, in superalloys, titanium and high temperature steels are joined together to form the major sub‐assemblies of the engine.

EVEN the technical press is inclined to devote more space to developments in aircraft and their component parts than to the metals and materials employed in their construction. In this article the writer proposes to survey the entire field of aircraft metals developed of recent years.

This study aims to control the oxidation resistance of Co-based deformed superalloys by adding trace elements Hf and Si.

The effects and mechanism of trace elements Hf and Si on the oxidation behavior of Co-Ni-Al-W-based forged superalloys were investigated by cyclic oxidation at 900°C.

The results show that the addition of trace elements Hf and Si does not affect the type of surface oxides of Co-Ni-based superalloys, and the oxidation layers of the alloys are TiO₂, spinel, Cr₂O₃, TaTiO₄, Al₂O₃ and TiN from outside to inside. However, the addition of elements can affect the activity of Cr and Ti elements; decrease the formation of TiO₂ and TaTiO₄ layers, which are harmful to the oxidation performance; and then improve the oxidation resistance of the alloy.

The relevant research results can not only optimize the microalloying element content of Co-Ni-Al-W-based superalloys, but also provide a new perspective for the composition optimization design of superalloys.

The purpose of this paper is to machine the pressure surface of the turbine blade made of A286 iron-based superalloy by using four directions of raster strategy, including horizontal upward, horizontal downward, vertical upward and vertical downward, to achieve appropriate surface roughness and to investigate the tool wear in each strategy.

In this study, all cutting tests were performed by DAHLIH-MCV 1020 BA vertical 3-axis machining center with ball nose end mill. After milling by each strategy, according to the surface slope, the surface was divided into 27 meshes, and roughness of surface was studied and compared. Roughness measuring after machining was implemented by using portable Mahr ps1 roughness tester, and surface texture was photographed by CCD 100× optical zoom camera. Also, to measure tool flank wear in each strategy as an indication of tool life, the surface of workpiece was divided into four equal areas. The wear of the inserts was measured by ARCS vertical non-contact measuring system at the end of each area.

The results indicate that cutting directions and toolpath strategies have significant influence on tool wear and surface roughness in machining processes and that they can be taken into consideration individually as determinative parameters. In this case, the most uniform surface texture and the lowest surface roughness are obtained by using horizontal downward direction; in addition, abrasion is a dominant tool wear mechanism in all experiments, and tool wear in the horizontal downward is lower than other strategies.

Machining of turbine blades or other airfoil-shaped workpieces is quite common in manufacturing aerospace and aircraft products. The results of this research contribute to increasing quality of machined surface and tool life in machining of turbine blade.

This work proves the significance of milling strategies in machining of the turbine blade made of A286 superalloy and, consequently, exhibits the proper strategy in terms of surface roughness and tool life. Also, this work explains and elaborates the behavior of A286 superalloy in machining processes, which has not been studied much in recent research works.

Specialist surface treatment subcontractor, Impact Finishers Limited, has been awarded BS 5750 Part II, and is believed to be the first company of its kind to receive this coveted British Standard qualification.

This paper focuses on recent advances in direct freeform fabrication of high performance components via selective laser sintering (SLS). The application, known as SLS/HIP, is a low cost manufacturing technique that combines the strengths of selective laser sintering and hot isostatic pressing (HIP) to rapidly produce low volume or “one of a kind” high performance metal components. Direct selective laser sintering is a rapid manufacturing technique that can produce high density metal parts of complex geometry with an integral, gas impermeable skin. These parts can then be directly post‐processed by containerless HIP. The advantages of in situ encapsulation include elimination of a secondary container material and associated container‐powder interaction, reduced pre‐processing time, a short HIP cycle and reduction in post‐processing steps compared to HIP of canned parts. SLS/HIP is currently being developed under a DARPA/ONR program for INCONEL® 625 superalloy and Ti‐6Al‐4V, the demonstration components being the F‐14 turbine engine vane and the AIM‐9 missile guidance section housing base respectively.