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.

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

This paper presents an overview of the recent advances in high performance cutting of aerospace alloys and composite currently used in aeroengine and aerostructure applications. Progress in cutting tool development and its effect on tool wear and surface integrity characteristics of difficult to machine materials such as nickel based alloys, titanium and composites is presented. Further, advances in cutting technologies are discussed, focusing on the role of hybrid machining processes and cooling strategies (MQL, high pressure coolant, cryogenic) on machining performance. Finally, industrial perspectives are provided in the context of machining specific components where future challenges are discussed.

High performance cutting of advanced aerospace alloys and composite materials

A review on machinability of carbon fiber reinforced polymer (CFRP) and glass fiber reinforced polymer (GFRP) composite materials

Delamination formation, evaluation and suppression during drilling of composite laminates: A review

The aerospace industry has experienced significant growth over the past decade and it is estimated that nearly 30,000 new commercial passenger aircraft will be required by 2030 to meet rising global demand. Abrasive machining is a key material removal process utilised in the production of aeroengine components. Current industrial practice and perspectives relating to grinding in the aerospace sector are presented including general workpiece surface integrity standards/requirements, fluid delivery systems, wheel preparation options and machine tool designs/configurations. Corresponding academic research on the machinability of aerospace alloys and composites are critically reviewed together with recent developments involving novel/innovative grinding processes.

Abrasive machining of advanced aerospace alloys and composites

Modern Machining of Advanced Aerospace Alloys - Enabler for Quality and Performance

Five different coatings and two PCBN grades were evaluated when high speed turning Inconel 718. Tool life was 40% higher when employing TiSiN coated over uncoated inserts at 200 m/min. When operating at 300–450 m/min however, coatings provided no appreciable benefit. Workpiece surface roughness varied between ∼0.25 and 1.05 μm Ra while cutting forces were

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High speed turning of Inconel 718 using PVD-coated PCBN tools

A method for the manufacture of a cutting tool provided with a tool holder ( 1 ) to which a cutter ( 2 ) is separably attached, includes applying a generative production process to a tool base body ( 3 ) to create the tool holder ( 1 ) with a desired finished shape.

Method for the manufacture of a cutting tool

Production of cutting tools with a holder (1) in which a removable cutter (2) is mounted comprises treating a tool base (3) using a generative manufacturing process to produce the final shape of the holder.

Method of manufacturing a cutting tool, which has a basis part, the latter being put in the final form of the tool's holder through the use of a generative finishing process

Gregor Kappmeyer

Papers

High performance cutting of advanced aerospace alloys and composite materials

Modern Machining of Advanced Aerospace Alloys - Enabler for Quality and Performance

High speed turning of Inconel 718 using PVD-coated PCBN tools

Method for the manufacture of a cutting tool

Method of manufacturing a cutting tool, which has a basis part, the latter being put in the final form of the tool's holder through the use of a generative finishing process