Core/Shell Nanoparticles: Classes, Properties, Synthesis Mechanisms, Characterization, and Applications

Titanium and nickel alloys represent a significant metal portion of the aircraft structural and engine components. When these critical structural components in aerospace industry are manufactured with the objective to reach high reliability levels, surface integrity is one of the most relevant parameters used for evaluating the quality of finish machined surfaces. The residual stresses and surface alteration (white etch layer and depth of work hardening) induced by machining of titanium alloys and nickel-based alloys are very critical due to safety and sustainability concerns. This review paper provides an overview of machining induced surface integrity in titanium and nickel alloys. There are many different types of surface integrity problems reported in literature, and among these, residual stresses, white layer and work hardening layers, as well as microstructural alterations can be studied in order to improve surface qualities of end products. Many parameters affect the surface quality of workpieces, and cutting speed, feed rate, depth of cut, tool geometry and preparation, tool wear, and workpiece properties are among the most important ones worth to investigate. Experimental and empirical studies as well as analytical and Finite Element modeling based approaches are offered in order to better understand machining induced surface integrity. In the current state-of-the-art however, a comprehensive and systematic modeling approach based on the process physics and applicable to the industrial processes is still missing. It is concluded that further modeling studies are needed to create predictive physics-based models that is in good agreement with reliable experiments, while explaining the effects of many parameters, for machining of titanium alloys and nickel-based alloys.

Machining induced surface integrity in titanium and nickel alloys: A review

Surface integrity in material removal processes: Recent advances

The increasing attention to the environmental and health impacts of industry activities by governmental regulation and by the growing awareness in society is forcing manufacturers to reduce the use of lubricants. In the machining of aeronautical materials, classified as difficult-to-machine materials, the consumption of cooling lubricant during the machining operations is very important. The associated costs of coolant acquisition, use, disposal and washing the machined components are significant, up to four times the cost of consumable tooling used in the cutting operations. To reduce the costs of production and to make the processes environmentally safe, the goal of the aeronautical manufacturers is to move toward dry cutting by eliminating or minimising cutting fluids. This goal can be achieved by a clear understanding of the cutting fluid function in machining operations, in particular in high speed cutting, and by the development and the use of new materials for tools and coatings. High speed cutting is another important aspect of advanced manufacturing technology introduced to achieve high productivity and to save machining cost. The combination of high speed cutting and dry cutting for difficult-to-cut aerospace materials is the growing challenge to deal with the economic, environmental and health aspects of machining. In this paper, attention is focussed on Inconel 718 and recent work and advances concerning machining of this material are presented. In addition, some solutions to reduce the use of coolants are explored, and different coating techniques to enable a move towards dry machining are examined.

A review of developments towards dry and high speed machining of Inconel 718 alloy

Nickel-based superalloy is widely employed in aircraft engines and the hot end components of various types of gas turbines with its high strength, strong corrosion resistance and excellent thermal fatigue properties and thermal stability. However, nickel-based superalloy is one of the extremely difficult-to-cut materials. During the machining process, the interaction between the tool and the workpiece causes the severe plastic deformation in the local area of workpiece, and the intense friction at the tool–workpiece interface. The resulting cutting heat coupled with the serious work hardening leads to a series of flaws, such as excessive tool wear, frequent tool change, short tool life, low productivity, and large amount of power consumption etc., in which the excessive tool wear has become one of the main bottlenecks that constraints the machinability of nickel-based superalloys and its wide range of applications. In this article, attention is mainly focused on the tool wear characteristics in the machining of nickel-based superalloys, and the state of the art in the fields of failure mechanism, monitoring and prediction, and control of tool wear are reviewed. The survey of existing works has revealed several gaps in the aspects of tool self-organizing process based on the non-equilibrium thermodynamics, tool wear considering the tool nose radius, thermal diffusion layer in coated tools, tool life prediction based on the thermal–mechanical coupling, and industrial application of tool wear online monitoring devices. The review aims at providing an insight into the tool wear characteristics in the machining of nickel-based superalloys and shows the great potential for further investigations and innovation in the field of tool wear.

Tool wear characteristics in machining of nickel-based superalloys

Multi-response ANN modelling and analysis on sliding wear behavior of Al7075/B4C/fly ash hybrid nanocomposites

A novel approach for the production and characterisation of aluminium-alumina hybrid metal matrix composites

Machining of novel light weight 7075 aluminum alloy reinforced with thin-walled hollow ceramic bubbles present a significant challenge to the manufacturing industry. The presence of hollow bubble p...

Machining of novel AA7075 foams containing thin-walled ceramic bubbles

The goal of the present study is to develop a thin film hydrous ruthenium oxide (RuO2) electrode material on Ni flashed AISI 317 stainless steel (SS) substrate by pulse electrodeposition (PED) technique for application in supercapacitors. The nickel (Ni) strike thin film is deposited prior to RuO2 in order to improve the adhesion of the active material on the SS substrate. The prepared RuO2 active material on Ni strike SS electrode is characterized using XRD, SEM with EDAX and electrochemically using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) using an IVIUM reference potentiostat. The surface morphologies of the thin film (thickness of 2.3 μm) active materials are nano-spherical shaped and the particles are arranged uniformly without cracks on the SS substrate. The electrochemical impedance and CV profile demonstrates its superior characteristics in the electrochemical system. Moreover, the specific capacitance of RuO2 value is approximately 520 F g− 1 at the scan rate of 1 mV s− 1 and it's indicating a better utilization of active species in supercapacitors.

Development of nano-spherical RuO2 active material on AISI 317 steel substrate via pulse electrodeposition for supercapacitors


 Aluminum metal matrix composites (MMC) find many industrial applications due to its high strength, zero corrosion, light weight and durability. In this work, gravity stir casting and squeeze stir casting were used to produce MMC solid rods of length 21cm. LM25 grade, from scrap alloy wheel of car, was used as matrix and Alumina was added as reinforcements to improve the composite properties. The performed microstructure analysis showed a greater percentage of porosity for gravity casted samples. Brinell hardness tests recorded 61 and 56 for squeeze and gravity stir casting respectively. The analysis was further strengthened by conducting tensile test, compression test, abrasion and erosive wear tests on the casted pipe sections. Optical Microscopy images of squeeze casted Al MMC’s shows a homogenous and a condensed LM25 matrix with alumina reinforcements even at high abrasion rates. Squeeze casted samples exhibited higher hardness, tensile and compression strengths and wear resistance by keeping stirring time, and stirring speed constant. Squeeze stir casting was suggested for the production of Aluminum MMC pipes.

Ramanathan Arunachalam

Papers

Multi-response ANN modelling and analysis on sliding wear behavior of Al7075/B4C/fly ash hybrid nanocomposites

A novel approach for the production and characterisation of aluminium-alumina hybrid metal matrix composites

Machining of novel AA7075 foams containing thin-walled ceramic bubbles

Development of nano-spherical RuO2 active material on AISI 317 steel substrate via pulse electrodeposition for supercapacitors

Mechanical and Tribological Evaluation of Aluminum Metal Matrix Composite Pipes Fabricated by Gravity and Squeeze Stir Casting