Metal degradation due to corrosion is a major challenge in most industries, and its control and prevention has to maintain a balance between efficiency and cost-effectiveness. The rising concern over environmental damage has greatly influenced this domain, as corrosion prevention should comply with the waste regulations of different regions. In this respect, a fundamental question is which modern synthetic materials are more viable from the point of view of their effectiveness. Therefore, this paper is aims to provide an advanced and holistic review of corrosion prevention and control methods. Corrosion prevention techniques have become extensive; however, the literature indicates that polymer coatings, nano-composite coatings, and encapsulation techniques consistently provide the most efficient and feasible outcomes. Therefore, this review article examined the phenomenon of corrosion inhibition mainly from the perspective of these three techniques. Moreover, this research utilized secondary qualitative methods to obtain data and information on comparative techniques. It is found that due to the rapid development of novel materials, corrosion inhibition techniques need to be developed on scales that are more general, so that they could be applied to varying environments. The self-healing coatings are generally based on epoxy-resins incorporated with synthetic compounds such as inhibitor ions, amino-acids, or carboxylic acids. These coatings have become more widespread, especially due to bans on several traditional prevention materials such as compounds of chromium (VI). However, self-healing coatings are comparatively more costly than other techniques because of their method of synthesis and long-term durability. Therefore, although self-healing nanomaterial-based coatings are viable options for limited usage, their utilization in large and complex facilities is limited due to the costs involved. Amino acids and other biological macro-molecules provide another option to attain environmental sustainability and long durability, especially due to their origins being most of naturally occurring compounds such as lignin, cellulose, and proteins.

The present paper deals with the mechanisms of chip formation during cutting operations. It deals with some experiments characterising the chip morphologies and microstructure chip investigations under high loadings. In this contribution, mechanisms of chip segmentation are presented. The effect of cutting conditions on cutting forces is treated. Consequently, the chip segmentation phenomenon was correlated to cutting forces evolutions. Also, an investigation on chip strain localisation is carried out. Numerical simulations dealing with chip formation and considering thermomechanical phenomena are also presented. Some numerical results related to chip formation based on the theory of strain gradient plasticity are also discussed. Moreover, the effect of machining system stiffness on chip segmentation is analysed.

Many efforts have been made over the years to minimize the usage of mineral oil-based MWFs. This includes the trail of its alternatives, such as vegetable oil-based MWFs, nanofluids, etc. These alternatives have shown comparable results to mineral oil-based MWFs in producing a better surface finish and machining efficiency. Apart from the conventional flooding of MWFs, several alternative techniques have been developed by researchers to minimize or eliminate the usage of MWFs, including dry machining, high pressure coolant technique, minimum quantity lubrication, etc. which have also demonstrated promising results. This review attempts to highlight the drawbacks of mineral oil-based MWFs and to assess the applicability of vegetable oil-based MWFs in machining applications. Furthermore, other sustainable machining techniques are discussed in the literature review section, which highlight the main issues associated with the mentioned machining operations and their shortcomings based on the most recent literature. From the comprehensive and critical review that was performed, we inferred that the alternative methods are not mature enough at this stage and that they fall behind in some associated outcomes, some of which may be the tribological properties, surface finish or surface roughness, the cutting forces, the amount of working fluid consumed, etc. More efforts are still needed to fully eliminate the use of MWFs. Moreover, the applications of nanofluids in machining operations have been reviewed in this paper. We concluded from the critical review that nanofluids are an emerging technology which have found their place in machining applications due to their excellent thermophysical properties, but are still in their developmental stage, and more detailed studies are needed to make these a cost-effective solution.

Mechanical properties of the metals and their alloys are influenced by the material grain size at microscale. In the present study, the Johnson-Cook (JC) material model is modified to incorporate the effect of material's grain size along with the plasticity coupled damage model. 2D finite element (FE) simulations of turning process of an aerospace grade aluminium alloy 2024 (AA2024) were performed with different grain sizes using a commercial FE software, ABAQUS/Explicit. FE simulation results were compared with the published experimental data on turning process of AA2024. The proposed modified JC material model successfully simulated the increase in cutting force as a function of grain size refinement.