Animesh Basak

Machining and tool wear mechanisms during machining titanium alloys

This paper investigates the machining mechanism of titanium alloys and analyses those understandings systematically to give a solid understanding with latest developments on machining of titanium alloys. The chip formation mechanism and wear of different cutting tools have been analyzed thoroughly based on the available literature. It is found that the deformation mechanism during machining of titanium alloys is complex and it takes place through several processes. Abrasion, attrition, diffusion–dissolution, thermal crack and plastic deformation are main tool wear mechanisms.

Electrical discharge machining of 6061 aluminium alloy

The wire electrical discharge machining (EDM) of 6061 aluminium alloy in terms of material removal rate, kerf/slit width, surface finish and wear of electrode wire for different pulse on time and wire tension was studied. Eight experiments were carried out in a wire EDM machine by varying pulse on time and wire tension. It is found that the material removal rate increases with the increase of pulse on time though the wire tension does not affect the material removal rate. It seems that the higher wire tension facilitates steady machining process, which generates low wear in wire electrode and better surface finish. The surface roughness does not change notably with the variation of pulse on time. The appearance of the machined surfaces is very similar under all the machining conditions. The machined surface contains solidified molten material, splash of materials and blisters. The increase of the pulse on time increases the wear of wire electrode due to the increase of heat input. The wear of wire electrode generates tapered slot which has higher kerf width at top side than that at bottom side. The higher electrode wear introduces higher taper.

Weldability of duplex stainless steel

Duplex stainless steels (DSSs) have many advantages due to the unique structural combination of ferrite and austenite grains. The structural change of these materials is very complex during welding, and it deteriorates the functional properties. This research investigates different welding processes such as laser beam, resistance, tungsten inert gas, friction stir, submerged arc, and plasma arc weldings considering the research available in the literature. The welding mechanism, change of material structure, and control parameters have been analyzed for every welding process. This analysis clearly shows that DSS melts in all most all welding processes, but the thermal cycle and maximum heat input are different. This difference affects the resulting structure and functional properties of the weld significantly.

Effect of reinforced particle size on wire EDM of MMCs

This paper investigates the effect of the size of reinforced particles on wire electrical discharge machining (EDM) of metal matrix composites (MMCs) in terms of material removal rate (MRR), surface integrity and wear of wire electrodes (WEs). It was found that larger particles significantly reduced the MRR, as they were better able to protect the matrix material from EDM sparks compared to smaller particles. The machined surfaces were full of solidified melted matrix, splashes of melted material, cavities and blisters, which are not significantly affected by particle size. Spattering and splashing might have contributed to the transfer of materials between the WE and the MMCs. The diameter of the WE was reduced nonlinearly with the increased size of the reinforced particles after machining. The smallest reduction in electrode diameter occurred in the unreinforced matrix material.

Effect of Al and Cr addition on tribological behaviour of HVOF and APS nanostructured WC–Co coatings

Abstract Nanostructured WC–Co based coatings were investigated. The main focus was given to the effect of Al and Cr addition on their tribological behaviour. These coatings were successfully deposited from engineered nanosized powders using high velocity oxy fuel (HVOF) and atmospheric plasma spraying (APS). Porosity level was <3%. Crystal sizes of around 20–30 nm determined by TEM in such coatings, confirm the retention of a nanosize after thermal spraying. The nanostructured coatings were tested for their tribological characteristics and compared to industrial micrometre sized WC–Co coatings and common wear resistant engineering materials. It was found that decarburisation of the coating constituents is a critical issue and has a large impact on the tribological behaviour of the coatings. Proper selection of spraying technique, spraying parameters and distribution of phases are shown to be key factors for achieving nanostructured coatings with high wear resistance.

Failure Mechanisms of Nanoparticle Reinforced Metal Matrix Composite

The quest for the advanced functional material of superior functionality for advanced structure is being driven in various fronts of engineering materials. One of such front is metal matrix composite (MMC) which has already been proven as one of the most productive field in that respect. With the advance of technology, now it is possible to reinforce the MMCs with nanosized particles compared to conventional micron-sized ones. However, the addition of nanoparticle in the MMC to improve its mechanical properties is not unconditional. To achieve positive gain by adding nanoparticles in the MMCs, all the influencing factors should be taken into consideration. The present paper reviews the failure mechanisms of nanoparticles reinforced MMCs in light of its strengthening mechanisms.

Accuracy and finish during wire electric discharge machining of metal matrix composites for different reinforcement size and machining conditions

Electric discharge machining has been established as an effective alternative process to conventional material removal processes for machining reinforced metal matrix composites. Wire cut electric discharge machining holes were produced in a metal matrix composite (10 vol% of SiC in Al6061), which were then investigated to determine the machinability of the material using this process. It was observed that the input factors such as the size of reinforced particles, wire tension and pulse-on time significantly affect diameter error, circularity and surface roughness. Pulse-on time, the interaction between pulse-on time and wire tension contribute to the maximum diameter error. The wire tension is the most significant factor to circularity, which is followed by the interaction between pulse-on time. In particular, wire tension with low and high tensions results in poor circularity. It has been found that there are more surface defects encountered when particle sizes are smaller, and circularity is improved when particles are in a medium size. In addition, the surface defect is reduced as the particles increase the melting resistance of the surface. The higher pulse-on time leads to higher heat and more time to degrade the surface. Therefore, low pulse-on time and wire tension gave better surface finish.

Quantitative prediction of phase transformations in silicon during nanoindentation

This paper establishes the first quantitative relationship between the phases transformed in silicon and the shape characteristics of nanoindentation curves. Based on an integrated analysis using TEM and unit cell properties of phases, the volumes of the phases emerged in a nanoindentation are formulated as a function of pop-out size and depth of nanoindentation impression. This simple formula enables a fast, accurate and quantitative prediction of the phases in a nanoindentation cycle, which has been impossible before.

Tool wear and surface quality of metal matrix composites due to machining: A review

Higher tool wear and inferior surface quality of the specimens during machining restrict metal matrix composites’ application in many areas in spite of their excellent properties. The researches in this field are not well organized, and knowledge is not properly linked to give a complete overview. Thus, it is hard to implement it in practical fields. To address this issue, this article reviews tool wear and surface generation and latest developments in machining of metal matrix composites. This will provide an insight and scientific overview in this field which will facilitate the implementation of the obtained knowledge in the practical fields. It was noted that the hard reinforcements initially start abrasive wear on the cutting tool. The abrasion exposes new cutting tool surface, which initiates adhesion of matrix material to the cutting tool and thus causes adhesion wear. Built-up edges also generate at lower cutting speeds. Although different types of coating improve tool life, only diamond cutting tools show considerably longer tool life. The application of the coolants improves tool life reasonably at higher cutting speed. Pits, voids, microcracks and fractured reinforcements are common in the machined metal matrix composite surface. These are due to ploughing, indentation and dislodgement of particles from the matrix due to tool–particle interactions. Furthermore, compressive residual stress is caused by the particles’ indentation in the machined surface. At high feeds, the feed rate controls the surface roughness of the metal matrix composite; although at low feeds, it was controlled by the particle fracture or pull out. The coarser reinforced particles and lower volume fraction enhance microhardness variations beneath the machined surface.

Effect of machining parameters on deformation behaviour of Al-based metal matrix composites under tension

The effects of machining parameters, such as reinforcement size, machining speed and feed rate, on tensile strength, strain at break and fractured surfaces of Al-based metal matrix composites were analysed in this present investigation. It was found that larger particles (13 µm) induce higher stiffness on machined metal matrix composite parts machined at higher speed (2500 r/min) and lower feed (200 mm/min), providing constant input parameters are of low values and vice versa. The effect of reinforcement size on tensile strength is negligible and higher speed (2500 r/min) and lower feed (200 mm/min) give higher tensile strength when constant input parameters are of low values. The higher machining speed (2500 r/min) gives higher strain at break though reinforcement size and feed rate have minor effect on strain at break when the constant input parameters are of high values. When the constant input parameters are of low values, the smaller reinforcement (0.7 µm), machining speed (1500 r/min) and feed rate (200 mm/min) give higher strain at break. Ductile fracture occurs in all cases regardless of input variables and smaller nodules were formed on fractured surface in the case of smaller particle (0.7 µm)-reinforced metal matrix composites.