The machinability of materials is highly affected by their hardness, and it affects power consumption, cutting tool life as well as surface quality while machining the component. This work deals with machining of annealed AISI 4340 alloy steel using a coated carbide tool under a dry environment. The microhardness of annealed and non-annealed workpieces was compared and a significant reduction was found in the microhardness of annealed samples. Microstructure examination of the annealed sample revealed the formation of coarse pearlite which indicated a reduction of hardness and improved ductility. A commercially CVD multilayer (TiN/TiCN/Al₂O₃/ZrCN) coated cemented carbide cutting tool was employed for turning quenched and tempered structural AISI 4340 alloy steel by varying machining speed, rate of feed, and depth of cut to evaluate the surface quality, machining forces, flank wear, and chip morphology. According to the findings of experiments, the feed rate possesses a high impact on surface finish, followed by cutting speed. The prominent shape of the serrated saw tooth chip was noticed at a higher cutting speed. Machined surface finish and cutting forces during turning is a function of the wear profile of the coated carbide insert. This study proves that annealing is a low-cost and economical process to enhance the machinability of alloy steel.

Air plasma cutting technology is widely used for high-speed profiling of electrically conductive materials. The cut quality of surface and thermal effects is highly influenced by gas composition and process parameters. This study aims to systematically optimise and comparatively evaluate conventional compressed-air plasma cutting and an oxygen-assisted compressed-air plasma cutting process for 10 mm thick C-20 carbon steel plates. The investigation was conducted in two sequential stages using statistical Design of Experiments (DoE). First, a full-factorial design comprising 20 experiments was performed using compressed air to establish baseline process parameters and optimum operating ranges. Subsequently, a Central Composite Design (CCD) based on Response Surface Methodology (RSM) was employed for 20 additional experiments to model and compare pure compressed air with an oxygen-compressed air mixture. Cut quality was evaluated in terms of kerf width, dross height, bevel angle, surface roughness, maximum cutting temperature, and heat-affected zone (HAZ) length. The results demonstrate that the addition of oxygen improves plasma arc characteristics and produces substantial reductions in kerf width from 2.3 to 2.1 mm, dross height from 0.3 to 0.2 mm, bevel angle from 1.6 to 1.4 Radian, Avg.surface roughness from 1.2 to 0.2 µm, Max.surface roughness from 8.2 to 1.6 µm, Max. surface temperature from 1719.3 to 1607.8 °C and HAZ from 38 to 23.2 µm compared with conventional compressed-air cutting. Furthermore, microstructural analysis of the cut surfaces revealed a significant reduction in HAZ length when the oxygen-assisted gas mixture was employed. Overall, the findings demonstrate the potential of oxygen-assisted compressed-air plasma cutting to improve cutting efficiency and surface quality while reducing thermal effects, providing practical guidance for the optimisation of plasma-assisted manufacturing processes.

A cutting tool is a primary element to remove materials from the workpiece and to produce the required shape and size. Rapid developments in technology required the machining of hardened metals, alloys, ceramics composites, and advanced materials using cutting tools. To ease the metal removal operation, different types of textures on cutting tools were introduced by many researchers using different machining processes, and continual research is underway in this area. This chapter reports on recent advances in texturing on cutting tools for turning, drilling, milling, grinding, and sawing operations. The applications of micro-plasma transferred arc, laser surface texturing, micro grinding, micro-electrical-discharge machining, focused ion beam machining, ultrasonic machining, micro indentation, and chemical etching processes to create different types of textures on various tooling materials for machining a wide range of materials in different cutting conditions are summarized for easy reference. The machining aspect of a textured tool for various materials, such as alloy steel, stainless steel, aluminum alloy, titanium alloys, and composites, is also included. The impact of textured cutting tools on cutting forces, surface finish, chip morphology, tool wear, cutting temperature, and machine power consumptions are discussed in detail along with major findings. This chapter will be very useful for researchers, academicians, and industrialists working in the field of precise turning and finishing of industrial components.