Hard and brittle materials (HBMs) are widely employed across various industries due to their exceptional mechanical properties. However, their inherently high hardness and brittleness pose significant challenges in machining, often resulting in surface and subsurface damage during production, particularly in mechanical operations. Such damage degrades surface roughness and compromises overall surface integrity. Laser polishing has emerged as a promising solution to mitigate fabrication-induced defects and enhance both surface quality and accuracy. This review examines recent advances in laser polishing of HBMs, focusing on the principles of laser polishing mechanism, heat transfer and fluid flow including analytical and numerical modelling. Also, experimental studies to enhance surface integrity including surface roughness, morphology, microstructure, and hardness are discussed. The paper concludes by outlining potential future directions and research prospects aimed at overcoming current limitations and further advancing laser polishing techniques for HBMs.

Carbon fiber-reinforced polymer (CFRP) structures have been increasingly used in various aerospace sectors due to their outstanding mechanical properties in recent years. However, the poor machinability of CFRP plates, combined with the inhomogeneous behavior of fibers, poses a challenge for manufacturers and researchers to define the critical factors and conditions necessary to ensure the quality of holes in CFRP structures. This study aims to analyze the effect of drilling parameters on CFRP delamination and to predict hole quality using a regression-based approach. The design of the experiment (DOE) was conducted using Taguchi’s L9 3-level orthogonal array. The input drilling variables included the feed rate, spindle speed, and three different drill types. A regression-based model using partial least squares (PLS) was developed to predict delamination defects during the drilling of CFRP plates. The PLS model demonstrated high accuracy in predicting delamination defects, with a Mean Squared Error (MSE) of 0.0045, corresponding to an accuracy of approximately 99.6%, enabling the rapid estimation of delamination. The model’s predictions were closely aligned with the experimental results, although some deviations were observed due to tool inefficiencies, particularly with end mill cutters. These findings offer valuable insights for researchers and practitioners, enhancing the understanding of delamination in CFRPs and identifying areas for further investigation.

Environmental side effects of machining lubricants are the main reasons for the progressive development of utilizing the minimum quantity lubrication (MQL) method instead of conventional methods. Owing to the high specific energy of cutting and generation of more heat in grinding, the MQL technique has a lower efficiency than conventional methods. However, by adding nanoparticles to the base oil, the lubrication efficiency in grinding can be enhanced. In this research, grinding of cold work tool steel AISI D2 was studied using a MQL technique by adding MoS2 and CuO nanoparticles to two types of vegetable-based oils: colza and soybean with different concentration percentages, and their effects were examined on the cutting forces (normal and tangential forces) and surface roughness. The results indicated that the values of normal force and tangential forces diminished by 19 and 35 % when using CuO nano powder in soybean base oil with a concentration of 4 % and MoS2 nano powder in soybean base oil with a concentration of 2 %, respectively. Furthermore, when using CuO nano powder in colza base oil and with a concentration of 2 %, the surface roughness had a significant reduction of 77 % in comparison with pure oil as a grinding fluid.

Rotational abrasive finishing (RAF) is a new nano-finishing technique in which the finishing forces are applied to the workpiece by the opposite rotations of a stirring-blades and the workpiece. The RAF process allows for finishing the inner and outer surfaces of workpieces, particularly complex ones with axial symmetry. The present study aims to propose a new theoretical model to obtain deeper insights into the material removal mechanism, surface roughness prediction, and forces in RAF process. Since the abrasive-workpiece interaction is random and complex in nature in the RAF, some initial assumptions were considered. To validate the repeatability of the experimental results, the experiments were designed based on the Response surface method (RSM). To validate the new proposed theoretical model, a number of influential parameters were investigated. It was found that the stirring-blade speed (S), working gap (W), and abrasive grain size (A) had significant effects on Ra. The minimum surface roughness (Ra) was obtained to be 46.87 nm at a rotational speed of 600 rpm, a working gap of 1 mm, and grain size of 18 μm. The experimental results were relatively in good agreement with the theoretical results so that the maximum error was about 24%. This can be assumed that the most important explanation for the difference between the theoretical and experimental results can be attributed to the initial theoretical assumptions.

Nickel–Iron coating was formed from a sulfate base electroplating bath under a current density of 3 A/dm 2 and turbulence of 300 rpm on a previously prepared cylindrical steel substrate. In order to obtain a sample including nickel composite coating, different amounts of alumina particle powder were added to the plating solution of the sample in question. By adding different quantities of ferrous sulfate to the electroplating bath under a current density of 2.5 A/dm 2 and turbulence of 300 rpm, an optimal sample containing 20 g/L of ferrous sulfate was obtained was free of any stress and microcracks. A hardness test was performed for the optimal sample among the nickel–iron​ composite samples, and the sample containing 50 g/L of alumina particles was selected as the optimal sample. The Ni–Fe/Al 2O3 composite sample was tested for hardness, corrosion and wear. The obtained results showed that the highest hardness level is equivalent to 740 HV and the best corrosion resistance with the most positive corrosion potential. The lowest amount of wear mass is equal to 0.1 mg, and it showed the highest wear resistance.

Abstract Surface coating process is one of the techniques that increase the performance and service life of parts by increasing the mechanical properties. In this study, compared to the layered coating, a composite coating was done by electroplating method on stainless steel grade st37. The aim of this study was to increase the mechanical properties of the surface base metal as well as the coating. Materials characterization tests such as X-ray diffraction tests and imaging were performed by scanning electron microscopy. In addition, a Vickers microhardness test and wear resistance were performed. Chemical tests were done on the created coating, the results of which were presented as polarization and Varna quest diagrams. According to the results, the coating containing Ni-Fe/Al2O3 particles showed better mechanical properties so that by increasing the amount of alumina particles to 50 g/L, the hardness reached 750 (HV 0.5), which is 585 (HV 0.5) for the coating without alumina was reported. Varna quest chemical test reported that coat with alumina corroded 10 times less than st37 row material. The wear friction coefficient for row st37 was 0.21 however this amount after adding alumina to the coating structure reached 0.35.

Nickel–Iron coating was formed from a sulfate base electroplating bath under a current density of 3 A/dm 2 and turbulence of 300 rpm on a previously prepared cylindrical steel substrate. In order to obtain a sample including nickel composite coating, different amounts of alumina particle powder were added to the plating solution of the sample in question. By adding different quantities of ferrous sulfate to the electroplating bath under a current density of 2.5 A/dm 2 and turbulence of 300 rpm, an optimal sample containing 20 g/L of ferrous sulfate was obtained was free of any stress and microcracks. A hardness test was performed for the optimal sample among the nickel–iron​ composite samples, and the sample containing 50 g/L of alumina particles was selected as the optimal sample. The Ni–Fe/Al 2O3 composite sample was tested for hardness, corrosion and wear. The obtained results showed that the highest hardness level is equivalent to 740 HV and the best corrosion resistance with the most positive corrosion potential. The lowest amount of wear mass is equal to 0.1 mg, and it showed the highest wear resistance.

Ultra-precise finishing of parts with complicated geometry has faced many limitations using traditional methods due to the use of rigid tools. This study aims to introduce a new mechanism by developing a rotational abrasive finishing (RAF) operation, where the simultaneous rotation mechanism of a workpiece and the stirring-chamber is used in the opposite directions. In this paper, the associated velocities and forces in the developed RAF technique, the effects of stirring blades rotary speed, working gap as well as various meshing of abrasive grits on material removal ( increment m), surface roughness variation rate ( increment R-a) the percentage of surface improvement (% increment R-a), and the surface roughness value (R-a), on one of the most important cutting tools, i.e. drill bit, were examined. The research outcomes demonstrated that with increasing the speed of the stirring-chamber combined with the selecting larger abrasive grits, increment m and increment Ra will increase, while an increment in working gap resulted in a decrease in increment m and increment R-a. Also, reducing surface roughness from micrometer scale to nanometer (from initial value 547 nm to final value 69 nm) resulted in an 87% enhancement in the surface quality. Therefore, the superiority of RAF technique in ultrafinishing of various work parts can be demonstrated theoretically and experimentally.

It is difficult to attain a desirable surface quality at nanoscale using traditional finishing methods. Therefore, novel and more advanced methods known as nano-finishing have been introduced to overcome this limitation. This study addresses the Rotational Abrasive Finishing (RAF) process, one of the newest advanced nano-finishing techniques that involves simultaneous rotation of the stirrer and workpiece in opposite directions. This process is intended for finishing the interior surface of workpieces with ultra-high precision. Speeds and forces involved in the RAF process along with effects of rotational speeds of stirrer, working gap, and mesh size of the abrasive particles on material removal (Delta m), surface roughness (Ra), and change in surface roughness (Delta Ra) were studied on a stainless steel workpiece. The results indicated that material removal and change in surface roughness increased due to increase in stirrer speed while increasing working gap and abrasive mesh size reduced Am and Delta Ra. Moreover, surface roughness was found to be reduced from micro- to nano-scale hence final surface roughness was 51 am. Here by applying this new finishing method, the surface quality improvement was achieved by over 83%.

Traditional finishing techniques, including grinding, honing, and lapping have several disadvantages and limitations due to their solid and rigid tools with complex geometries. To overcome these limitations, modern techniques known as nanofinishing techniques are introduced. This paper presents a new micro/nanofinishing technique used in different industries, especially high-tech industries like aerospace, military applications, and auto-making industry. This technique is called rotational abrasive finishing (RAF) method. In this technique, the medium inside the cylindrical workpiece is rotated using a bladed stirring axis. The medium hits against the surface of the workpiece while rotating in the opposite direction. In this way, material removal and finishing operation are achieved. In order to avoid medium discharge, two caps, one in upper side and one in the bottom side of workpiece, are used. RAF technique makes it possible to reduce surface roughness and achieve roughness in nanometer scales so that on our test workpiece roughness was reduced from 0.283 to 88 nm, indicating 70% improvement in surface quality by applying 20 min machining duration. It was practically proved that RAF is a fast, efficient, and cost-effective finishing technique for different products by which it is possible to achieve ultra-precise surface quality at nanometeric scales.