Recent Advances in Turning Processes Using Coated Tools—A Comprehensive Review

Abstract

Turning continues to be the largest segment of the machining industry, which highlights the continued demand for turned parts and the overall improvement of the process. The turning process has seen quite an evolution, from basic lathes using solid tools, to complex CNC (Computer Numerical Control) multi-process machines, using, for the most part, coated inserts and coated tools. These coatings have proven to be a significant step in the production of high-quality parts and a higher tool life that have captivated the industry. Continuous improvement to turning coated tools has been made, with many researches focusing on the optimization of turning processes that use coated tools. In the present paper, a presentation of various recently published papers on this subject is going to be made, mentioning the various types of coatings that have recently been used in the turning process, the turning of hard to machine materials, such as titanium alloys and Inconel, as well as the interaction of these coatings with the turned surfaces, the wear patterns that these coatings suffer during the turning of materials and relating these wear mechanisms to the coated tool’s life expectancy. Some lubrication conditions present a more sustainable alternative to current methods used in the turning process; the employment of coated tool inserts under these conditions is a current popular research topic, as there is a focus on opting for more eco-friendly machining options.

Characteristics and Wear Mechanisms of TiAlN-Based Coatings for Machining Applications: A Comprehensive Review

“…As mentioned previously, the level of residual stresses inside the coatings impacts their properties and, thus, their machining performance [30,38,39,43]. There are some recent studies made on this topic, as the work presented by Hou et al [72], where the influence of compressive stresses on the TiAlN-coated tool's performance when milling Ti alloy Ti-6Al-4V was investigated.…”

“…Moreover, the control of the thickness throughout the substrates surface is also harder. These problems can be attenuated by using a different PVD process, such as pulsed high-power sputtering [30]. However, this can come at a cost, such as inducing excessive residual stresses in the coating or even sacrificing adhesive strength.…”

Cutting Forces Assessment in CNC Machining Processes: A Critical Review

“…Correct coating application is crucial for having a good machining process, as these coatings influence the wear rate of the tool and the quality of the machined part [12]. A wrong application or a poorly optimized process will influence the cutting forces generated during the machining process [13,14]. Having knowledge of how these forces influence the machining process is very important when it comes to process optimization, as these forces are directly correlated to certain aspects, such as surface finish quality, tool life, and energy consumption.…”

“…As previously mentioned, the monitoring of cutting forces is of great importance, not only to improve/optimize the machining process, but also to gain insight into the cutting behavior of some tools, or even achieve knowledge on the machining process itself. Furthermore, cutting force determination/monitoring can bring the improvement of some cutting-tool technology, such as the use of new types of coatings for cutting tools [13,14], or even studying the influence of novel geometries, and how these will affect the cutting forces generation. -Simulation process is time-consuming and may take several hours of computing time; -Harder to implement than cutting force sensing systems (i.e., dynamometers); -Highly reliable on previously collected data.…”

MQL Strategies Applied in Ti-6Al-4V Alloy Milling—Comparative Analysis between Experimental Design and Artificial Neural Networks

“…It uses a small amount of cutting fluid in the form of an oil mist that is directly sprayed to the contact zone, helping to reduce friction and cutting forces, and decreasing the surface’s crumple zone by a large amount (~50%) when compared with dry cutting [ 21 ]. Consequently, MQL reduces tool wear [ 22 , 23 ]. This technique combines the lubrication from the cutting fluid and the cooling from the air pressure, sometimes reducing the thermal shock caused by flood lubrication [ 24 ], and can be used in drilling, milling, turning, and others.…”