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

In the pursuit toward achieving dry cutting, air machining, minimum quantity lubrication (MQL), and cryogenically cooled machining are the stepping stones. Nevertheless, machining is always accompanied by certain difficulties, and hence none of these methods has provided a complete solution. Hence, this article reviews various MQL methods used by various machining processes for different materials. It also highlights the future work directions for research in this area.

A Review on Minimum Quantity Lubrication for Machining Processes

https://hal.archives-ouvertes.fr/hal-02417879/document

Recent advances in drilling hybrid FRP/Ti composite: A state-of-the-art review

The researchers have worked on many facets of machining of hardened steel using different tool materials and came up with their own recommendations. Researchers have tried to investigate the effects of cutting parameters, tool materials, different coatings and tool geometry on different machinability aspects like, the tool life, surface roughness, cutting forces, chip morphology, residual stresses and the tool–chip interface temperature under dry and/or semi-dry and/or flood cooling environment during machining of hardened steels while many of them have ventured to characterize the wear phenomenon. Good amount of research has been performed on an analytical and/or numerical and/or empirical modeling of the cutting forces, tool–chip interface temperature, and tool wear under orthogonal/oblique cutting conditions during machining of hardened steels. This paper presents a comprehensive literature review on machining of hardened steels using coated tools, studies related to hard turning, different cooling methods and attempts made so far to model machining performance(s) so as to give proper attention to the various researcher works.

Machining of hardened steel—Experimental investigations, performance modeling and cooling techniques: 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

Wear performance of (nc-AlTiN)/(a-Si3N4) coating and (nc-AlCrN)/(a-Si3N4) coating in high-speed machining of titanium alloys under dry and minimum quantity lubrication (MQL) conditions

Minimum quantity lubrication is an alternative to realize machining titanium alloys both economically and ecologically. In order to apply minimum quantity lubrication more efficiently, an investiga...

An experimental investigation on effects of minimum quantity lubrication oil supply rate in high-speed end milling of Ti–6Al–4V:

This paper investigates the machinability of Ti-6Al-4V in conventional surface grinding using silicon carbide abrasive which includes grinding force, specific grinding energy, surface topography, surface residual stress, and metallurgical structure alteration. The experimental result indicated that grinding force ratio and specific energy would decrease when chip formation played a dominant role in the mechanism of grinding. Workpiece ground surface was free of crack but cutting traces and micro-grooves on ground surface were much more obvious under higher feed rate. Chemical reactions and physical change existed in grinding of titanium alloys. Ground surface was in a state of high tensile residual stress under the effect of three mainly aspects: plastic deformation, microstructure transformation, and thermal cycling of surface layer which played the major role. The machined surface experienced microstructure alteration on the top layer of ground surface and a heat-affected zone was observed.

https://rd.springer.com/content/pdf/10.1007%2Fs00170-011-3272-z.pdf

Experimental investigation on conventional grinding of Ti-6Al-4V using SiC abrasive

This paper presents a new flexible method referring to coupling response surface methodology (CRSM) to acquire optimum cutting parameters in machining of difficult-to-cut titanium alloy under minimum quantity lubrication (MQL) condition. Cutting speed, feed rate and depth of cut are designed as three factors by using the Taguchi method, which are also subject to several constraints including processing efficiency, cutting force and surface quality. In addition, turning experiments of titanium alloy were performed in order to set up the model based on Taguchi experimental design and multiple regression method. ANOVA was carried out to prove the adequacy of the developed mathematical model and the influences of cutting parameters on constraints were also observed. The results indicated that the feed rate was the dominant factor affecting surface roughness and cutting forces, which were minimized when the feed rate and depth of cut were set to the lowest level, while cutting speed was set to the highest level. Moreover, the predicted values obtained by CRSM were in good agreement with the experimental values, which indicated that CRSM was an effective method to determine optimum cutting conditions for machining process under MQL condition.

A coupling method of response surfaces (CRSM) for cutting parameters optimization in machining titanium alloy under minimum quantity lubrication (MQL) condition

The friction in end-milling of Ti-6Al-4V has a great effect on tool life and surface quality of workpiece. This paper focuses on the effects of minimum quantity lubrication (MQL) with high pressure air and dry cutting (without coolant) in performance, in terms of friction reduction, cutting force, and cutting temperature. The equivalent friction pressure coefficient method has been proposed to analyze the friction in this study. Comparative experiments were performed to investigate friction in milling titanium alloy (Ti-6Al-4V) under different cooling/lubrication conditions (dry, MQL, and high pressure air). The main results were as follows: (1) Compared with dry cutting, the application of MQL or high pressure air lead to drastic reduction in friction at lower cutting speed in end-milling of Ti-6Al-4V. Furthermore, MQL and high pressure air had similar performance in reducing friction. (2) At higher cutting speed, the cutting performances of three coolant supply strategies were slightly different. But, the efficiency of application of MQL and high pressure air in the high-speed cutting condition was not yet obvious. Moreover, it was shown that MQL can reduce the friction at the chip-tool interface when cutting parameters and matching parameters of MQL were chosen properly. Therefore, it appears that MQL and high pressure air can be alternative environment friendliness approaches to improve machinability of difficult-to-cut materials.

Zhi Qiang Liu

Papers

Wear performance of (nc-AlTiN)/(a-Si3N4) coating and (nc-AlCrN)/(a-Si3N4) coating in high-speed machining of titanium alloys under dry and minimum quantity lubrication (MQL) conditions

An experimental investigation on effects of minimum quantity lubrication oil supply rate in high-speed end milling of Ti–6Al–4V:

Experimental investigation on conventional grinding of Ti-6Al-4V using SiC abrasive

A coupling method of response surfaces (CRSM) for cutting parameters optimization in machining titanium alloy under minimum quantity lubrication (MQL) condition

Investigation of friction in end-milling of Ti-6Al-4V under different green cutting conditions