B. Ramamoorthy

Bio: B. Ramamoorthy is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Machining & Inconel. The author has an hindex of 15, co-authored 27 publications receiving 634 citations.

Machinability investigation of Inconel 718 in high-speed turning

Abstract: Superalloy Inconel 718 is widely used for many industrial applications due to its unique properties. However, machinability of the material is considered to be poor due to its inherent characteristics. The machinability studies of Inconel 718 had been carried out by earlier researchers mostly at low or medium cutting speed. Machinability indices used in such cases have the characteristics such as cutting force, surface roughness, cutting temperature, etc. In the case of high-speed machining of Inconel 718, machinability indices such as chip compression ratio (ζ), shear angle (Ф), surface integrity, and chip analysis are of prime importance. Most of the researchers have not given due consideration to these vital machinability indices necessary for understanding of high-speed cutting of Inconel 718. In this work, an experimental investigation was carried out to understand the behavior of superalloy Inconel 718 when machined with cemented tungsten carbide (K20) insert tool. The result and analysis of this work indicated that the above-mentioned machinability indices are important and necessary to assess the machinability of Inconel 718 material effectively during high-speed machining.

A study on the wear resistance of electroless Ni–P/Diamond composite coatings

Abstract: The ability to co-deposit particulate matter in a matrix of electroless nickel has led to a new generation of composite coatings Polycrystalline diamond is one of the many varieties of particulate matter that can be co-deposited Composite diamond coating is a regenerative layer of fine diamond particles dispersed in a hard electroless nickel matrix In this work, experiments have been carried out to study the effect of heat treatment, particle size and phosphorus content on the wear characteristics of the composite electroless coating containing diamond particles The results indicate substantial increase in wear resistance after the coated sample containing 9–10 wt% P content having fine diamond particle size is annealed around 350°C

Numerical generation of anisotropic 3D non-Gaussian engineering surfaces with specified 3D surface roughness parameters

Abstract: Three-dimensional surface roughness of mating parts of engineering assemblies has a significant influence on their functional behaviour. Studies on load bearing capacity in elastohydrodynamic contacts, gap flow analysis in precision hydraulic assemblies using modeled 3D fluid continuum micro gap geometry, etc., have made it possible to quantify the effect of certain 3D surface roughness parameters on frictional behaviour of the assemblies. This set forth the need for artificially generated three-dimensional engineering surfaces having prescribed roughness values for a better understanding and prediction of tribological problems. In this paper, an algorithm is developed for the numerical generation of three-dimensional anisotropic surfaces with prescribed 3D surface roughness parameters. The procedures employ either the Non-linear Conjugate Gradient Method (NCGM) or 2-D Digital Filter method. The results show that both the methods can adequately produce surfaces at small correlation distances, while at higher correlation distances the NCGM yields better results. Comparison between model-simulated output and measurement results of three-dimensional surface roughness of engineering surface show a good match, supporting the validity of the model.

Effect of cutting parameters on the degree of work hardening and tool life during high-speed machining of Inconel 718

Abstract: The use of superalloy Inconel 718 is increasing in most of the sophisticated applications like aircraft engines, industrial gas turbines, rocket engines, space vehicles, submarines, etc. Hence, in-depth understanding of this material helps to determine the ability of this material to withstand severe conditions of stress, temperature, corrosion, and controls its longevity and reliability. In the present work, an attempt has been made to study the relationship of degree of work hardening and tool life as a function of cutting parameters like cutting speed, feed, depth of cut, untreated tungsten carbide and postcryogenic-treated tool. Work hardening and tool life are the major factors which need to be controlled/improved to enhance the machinability characteristics of superalloy Inconel 718. A significant performance in tool life was observed due to cryogenic treatment given to tungsten carbide tool. Moreover, it was observed that optimized cutting parameters not only minimized/controlled work hardening characteristics but also improved tool life while high-speed machining of Inconel 718.

Characterization of DC magnetron sputtered diamond-like carbon (DLC) nano coating

Abstract: Development in vapor deposition techniques over the last two decades has led to the introduction of many advanced coatings for metal-cutting tools. This paper examines the characteristics of multilayer Ti, TiN, and diamond-like carbon (DLC) coatings deposited on standard tool substrates at varying sputtering parameters and conditions, such as power density, partial pressure, substrate temperature, and reactive gases. The characteristics of films were examined using an X-ray diffractometer, Raman microscope, surface profilometer (to measure the thickness of the coating), Rockwell hardness tester (to test adhesion), and a micro hardness tester. The pin-on-disc test setup was used to find the coefficient of friction of the coatings. The results indicated that a graded multilayer coating showed better adhesion to the substrates. It was observed that higher target power density resulted in an increase of micro hardness and crystalline planes of coating. Lattice constant matching among layers of coating, proper substrate preparation, and a sequence of cleaning processes are the crucial factors for the enhancement of adhesion strength.

Electroless nickel, alloy, composite and nano coatings – A critical review

Abstract: The development of metal deposition processes based on electroless nickel, alloy and composite coatings on various surfaces has witnessed a surge in interest among researchers, with many recent applications made possible from many excellent properties. In recent years, these coatings have shown promising corrosion and wear resistance properties and large number of newer developments became most important from macro to nano level applications. After a brief review of the fundamental aspects underlying the coating processes, this paper discusses in detail about different electroless nickel alloy, composite, nano plating, bath techniques, preparation, characterization, new depositing mechanism and their recent applications, including brief notes on difficult substrate and waste treatment for green environment. Emphasis will be onto their recent progress, which will be discussed in detail and critically reviewed.

State-of-the-art in surface integrity in machining of nickel-based super alloys

Abstract: Nickel-based super alloys are gaining more significance, now-a-days, with extensive applications in aerospace, marine, nuclear reactor and chemical industries. Several characteristics including superior mechanical and chemical properties at elevated temperature, high toughness and ductility, high melting point, excellent resistance to corrosion, thermal shocks, thermal fatigue and erosion are primarily responsible for wide domain of application. Nevertheless, machined surface integrity of nickel-based super alloys is a critical aspect which influences functional performance including fatigue life of the component. This review paper presents state-of-the-art on various surface integrity characteristics during machining of nickel-based super alloys. Influence of various cutting parameters, cutting environment, coating, wear and edge geometry of cutting tools on different features of surface integrity has been critically explained. These characteristics encompass surface roughness, defects (surface cavities, metal debris, plucking, smeared material, redeposited material, cracked carbide particles, feed marks, grooves and laps), metallurgical aspects in the form of surface and sub-surface microstructure phase transformation, dynamic recrystallisation and grain refinement and mechanical characteristics such as work hardening and residual stress. Microstructural modification of deformed layer, profile of residual stresses and their influence on fatigue durability have been given significant emphasis. Future research endeavour might focus on development of new grades, advanced processing techniques of the same to ensure their superior stability of microstructure and thermo-mechanical properties along with advanced manufacturing processes like additive manufacturing to achieve highest level of fatigue durability of safety critical components while maintaining acceptable surface integrity and productivity.

Electroless Ni-P composite coatings

Abstract: This review outlines the development of electroless Ni–P composite coatings. It highlights the method of formation, mechanism of particle incorporation, factors influencing particle incorporation, effect of particle incorporation on the structure, hardness, friction, wear and abrasion resistance, corrosion resistance, high temperature oxidation resistance of electroless Ni–P composite coatings as well as their applications. The improvement in surface properties offered by such composite coatings will have a significant impact on numerous industrial applications and in the future they will secure a more prominent place in the surface engineering of metals and alloys.

Influence of Tool Materials on Machinability of Titanium- and Nickel-Based Alloys: A Review

Abstract: Titanium and nickel alloys are the most commonly used in the demanding industries like aerospace, energy, petrochemical, and biomedical. These highly engineered alloys offer unique combination of heat resistance, corrosion resistance, toughness, high operating temperature, and strength-to-weight ratio. These alloys are termed as “Difficult to cut materials” because of their low machinability rating. They are difficult to machine because of properties like low thermal conductivity, high strength at elevated temperatures, and high chemical reactivity. Machining of titanium- and nickel-based alloys causes problems of surface integrity and selection of cutting tool materials that is always a challenge for manufacturers. In this work, machinability studies for titanium and nickel alloys are reviewed with reference to cutting tool materials, associated wear mechanisms, failure modes, and novel tooling techniques. It also discusses major surface integrity defects like carbide cracking, white layer formation, wor...

Application of digital image processing in tool condition monitoring: A review

Abstract: Tool condition monitoring is gaining a parallel development with the advancement of automatic manufacturing processes in the last thirty years due to the increasing need for improvement of product quality. The advances of digital image processing techniques used in tool condition monitoring are an important research interest due to the improvement of machine vision system, computing hardware and non-tactile application. In this paper, a review of development of digital image processing techniques in tool condition monitoring is discussed and finally a conclusion is drawn about required systematic research in this field.