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A CoCrFeNi high-entropy alloy (HEA) coating, enhanced with Al and Mo, was fabricated on Q235 steel using laser cladding technology. The synergistic enhancement effect of Al and Mo on the coatings was studied. The findings revealed that the CoCrFeNi coating mainly comprised the single-phase FCC. In contrast, the BCC and σ phases were observed when Al and Mo were individually doped. The simultaneous doping of both these elements resulted in a coating consisting of the BCC and σ phases. Mo addition led to grain refinement and increased the kernel average misorientation value; similarly, Al addition further enhanced these effects. The separate additions of Al and Mo significantly refined the microhardness and wear resistance of the coating. When both elements were added simultaneously, the microhardness and wear resistance of the coating were further enhanced, demonstrating the synergistic effects of Al and Mo on these characteristics. Moreover, the individual doping of Al and Mo decreased the Kp value and the oxide layer's thickness. Meanwhile, their combined addition reduced the Kp value by approximately 82.5 % and 89.8 %, respectively. During the initial oxidation stage, rapid oxidation of Al occurred, thereby decreasing the oxidation rate. In contrast, Mo facilitated the formation of Al2O3.

Laser melting deposition–produced Ti6Al4V additive manufacturingparts tend to manifest as coarse columnar grains. This paper optimises the laser pulse frequency to manage the microstructuralcharacteristics of Ti6Al4V parts and enhance their tensile properties and corrosion resistance. A fiber laser processing equipment with a laser power of 1200 W and a spot diameter of 2.0 mm was employed for all experiments, which provides pulsed lasers at 4, 40, 400, and 4000 Hz at a scanning speed of 8 mm/s and a duty cycle of 95 % for comparative research.The findings demonstrated that increasing the pulse frequency improved the deposition efficiency.An appropriate pulse frequency could promote the refinement and columnar-to-equiaxed transition (CET) of primary β grains.At 400 Hz, the Ti6Al4V-deposited parts yielded refined equiaxed grains.The average grain size in the middle of the sample was about 206.8 μm,and the microstructure mainly comprised fine α-laths in a lamellar structure, which yielded the best overall performance of the parts, with the ultimate tensile strength and elongation reaching 1083 MPa and 4.09 %, respectively.Therefore, improvingthe structural properties of partsby regulating the deposition process, which is conducive to the online regulation of the forming quality of laser deposition parts, is an effective and feasible approach.

Coarse β-columnar grains are often present in Ti–6Al–4V laser-additive-manufactured samples, resulting in anisotropic and inferior fatigue performance under dynamic loading. Fine-equiaxed grains (FEGs) with a mean grain size of approximately 139 μm were successfully obtained by a novel deposition strategy through coordinated regulation of direct energy deposition technological parameters. Microstructures were transformed from α′ martensite to α'' martensite. As a result, the comprehensive performance was significantly improved. Without the use of an argon atmosphere glovebox and post heat treatment, the tensile strength and elongation in the horizontal direction of the FEGs were 1091 MPa and 4.09%, respectively. The corrosion resistance was 11.71-fold higher than that of the coarse columnar grains (CCGs). Improving the microstructure and performance by optimizing pulsed laser parameters is simple, effective, and conducive to online regulation of the quality of laser additive samples.

This paper investigates the influence of the concentration and particle size of h-BN nanoparticles in a nanofluid on the surface integrity of 304 austenitic stainless steel during turning, focusing on the cutting force, friction coefficient, cutting temperature, surface roughness, surface residual stress, work hardening capacity, and 3D surface topography. The results show that, compared to dry cutting, the addition of 3 wt.% h-BN nanofluid can reduce the friction coefficient on the rake face by 38.9%, lower the cutting temperature by 43.5%, decrease the surface roughness by 53.8%, decrease the surface residual stress by 61.6%, and reduce the work hardening degree by 27.5%. Two-dimensional profiles and the 3D surface topography display a more balanced peak–valley distribution. Furthermore, by studying the effect of different h-BN particle sizes in nanofluids on the surface integrity of the machined workpiece, it was found that nanoscale particles have a greater tendency to penetrate the tool–chip interface than submicron particles. Moreover, the h-BN particles in the nanofluid play a “rolling effect” and “microsphere” effect, and the sesame oil will also form a lubricating oil film in the knife-chip contact area, thereby reducing the friction coefficient, reducing the cutting force, and improving the machining surface quality.

In this work, a high-frequency pulsed laser-welding process was successfully implemented to fabricate a Ti–6Al–4V alloy butt joint. The microstructure of each zone of the welded joint was systematically characterized by carrying out scanning electron microscopy and electron backscatter diffraction measurements. In addition, the corrosion resistance of the welded joint was tested using traditional electrochemical and local electrochemical methods, while the main factors affecting corrosion resistance and the mechanism of the galvanic corrosion were also thoroughly investigated. From the acquired results, it was demonstrated that the α′ martensitic phases constituted the microstructure in the fusion zone (FZ), where the grain size, grain orientation, and misorientation distribution of the different zones varied, and the α′ martensitic and bulk α covered the heat-affected zone (HAZ). The corrosion resistance in the HAZ was slightly better than that in the base material, and both were worse than that of the FZ, which was related to the phase type. In addition, the corrosion current density values of FZupper were about 1/4.6 and 1/2.6 those of FZmiddle and FZdown, respectively, which was attributed to differences in the grain size and grain orientation. The FZ was protected as a cathode during galvanic corrosion, which is of great importance for ensuring the service life of the component during practical applications.

In-situ V carbides reinforced Fe-based plasma arc cladding layers were prepared in the condition of air-cooled and water-cooled substrate, the microstructure, grain size and properties were comparatively studied. Results showed that microstructures of the two cladding layers were lath martensite. When the substrate was water-cooled, the residence times above 1495 °C decreased 46.3%, and the average cooling rates above 870°Cincreased 53.3%. The average grain size of the layers’ matrix and carbides was clearly refined from 3.12 to 1.39 μm and from 0.37 to 0.09 μm, respectively. Moreover, the depth of heat-affected zone reduced by 14.3%, and the dilution rate reduced by 16.90%. The comprehensive performances of the water-cooled cladding layer were obviously improved. The microhardness increased from 258 to 1040 HV0.2, the corrosion resistance increased 2.10 times and was about 13.75 times that of the low-carbon steel substrate.

To address the tracking control problem of the periodic motion fast tool servo system (FTS), we propose a control method that combines adaptive sliding mode control with closed-loop iterative learning control. Adaptive sliding mode control enhances the system’s robustness to external non-repetitive disturbances, and exponential gain iterative learning control compensates for the influence of periodic disturbances such as cutting force. The experimental results show that the proposed iterative learning controller based on adaptive sliding mode control can effectively eliminate the influence of various interference factors, achieve accurate tracking of the FTS system’s motion trajectory within a limited number of iterations, and ensure the stability of the system, which has the advantages of a fast convergence speed, high tracking accuracy, and strong robustness.

Dimple-textured surfaces of square arrays with different geometrical parameters (area density, diameter and depth) were prepared on the surface of GCr15 steel. The friction and wear experiments were carried out under the lubrication of Suspension of graphene and liquid crystal 4-n-pentyl-4'-cyano biphenyl (5CB). By controlling the area density, diameter and depth of the dimples, the lubrication performance of laser surface texturing under the condition of starved lubrication was analyzed, and the reducing friction and wear resistance mechanism of laser surface texture was preliminarily discussed. The lubrication performance of the dimple-textured surface is best when the depth of the dimple is 10 μm, the area density is 8%, and the diameter is 100 μm. The friction coefficient at this textured parameter is 0.031, which is a 32.6% decrease compared to the untextured surface (0.046). The reduction friction mechanism of the textured surface is mainly to improve load-bearing capacity, store lubricant, reduce contact area and secondary lubrication. Meanwhile, XPS analysis shows that during the friction, the graphene/5CB suspension has a tribochemical reaction in the textured surface, and a chemical reaction film is formed on the steel surface. The research results can provide theoretical guidance for the optimization of texture geometric parameters under different application conditions.

Molecular dynamics simulations allow to investigate the microscopic evolution of a structure, and can also point the way to tool material design. In this paper, the effect of adding CaF2 and CaF2@SiO2 on the Si3N4/TiC system is studied using molecular dynamics simulations. The results show that the system with the addition of CaF2@SiO2 to the model has a higher hardness than the system with the addition of CaF2. In order to obtain the optimum parameters for self-lubricating ceramic tools, the effect of adding different amounts of CaF2@SiO2 on the Si3N4/TiC system was investigated. The Si3N4/TiC/CaF2@SiO2 system achieved optimum mechanical properties when four CaF2@SiO2 were included in the model. By analyzing the effect of the sintering temperature on the system, it was deduced that the hardness achieved a maximum value of 15.89 GPa and the modulus of elasticity reached 132.53 GPa when the sintering temperature was at 2073 K. Based on this sintering parameter, the Si3N4/TiC/CaF2@SiO2 composite ceramic tool material was experimentally prepared with the mechanical properties of 15.66 GPa hardness and 128.08 GPa modulus of elasticity. The experimental results were consistent with the simulation results.

Cutting force in lathe work is closely related to tool wear and affects the turning quality. Direct measurement of the cutting force by measuring the strain of the tool holder is challenging because the tool holder design aims to be highly rigid in order to undertake large cutting forces. Accordingly, the most popular dynamometer designs modify the standard tool holder by decreasing the structural rigidity of the holder, which reduces the machining precision and is not widely accepted. In order to solve the issue of the low stiffness of the dynamometer reducing the machining precision, in this paper, the ultra-low strain on the tool holder was successfully detected by the highly sensitive semiconductor strain gauges (SCSG) adjacent to the blade cutting insert. However, the cutting process would generate much heat, which increases the force measuring area temperature of the tool holder by about 30 °C. As a result, the readout drifted significantly with the temperature changes due to the high temperature coefficient of SCSG. To solve this problem, the temperature on the tool holder was monitored and a BP neural network was proposed to compensate for temperature drift errors. Our methods improved the sensitivity (1.14 × 10−2 mV/N) and the average relative error of the BP neural network prediction (≤1.48%) while maintaining the original stiffness of the tool holder. The smart tool holder developed possesses high natural frequency (≥6 kHz), it is very suitable for dynamic cutting-force measurement. The cutting experiment data in the lathe work show comparable performance with the traditional dynamometers and the resolution of the smart tool holder is 2 N (0.25% of total range).

The addition of CaF2@SiO2 and SiC whiskers to ceramic tools can improve their flexural strength and fracture toughness, reduce surface damage, and improve their cutting performance. The cutting experiments showed that under the same cutting conditions, the surface roughness of the workpiece processed with the Al2O3/TiC/SiC/CaF2@SiO2 (ATSC10) tool was significantly lower than that of the workpiece processed with the Al2O3/TiC/ SiC (ATS) tool. Additionally, the main cutting force and cutting temperature when cutting with the ATSC10 tool were lower by 30 and 31.7%, respectively. These results were attributed to the precipitation of CaF2 from the nanocoated particles during cutting and the formation of a uniform and continuous lubricating film on the surface of the tool. The wear on the front surface of the ATS tool was mainly adhesive, and that on the back tool surface was mainly abrasive. For ATSC10, the main forms of wear on the tool front surface were adhesive and abrasive, whereas the main form of wear on the tool back surface was abrasive with slight adhesive wear. The addition of nano-coated particles and whiskers improved the mechanical properties of the cutting tool while maintaining good cutting performance.

We studied the effects of peak temperature and cooling rate in the secondary welding thermal cycles on the martensite/austenite (M/A) constituents’ characteristics (including fraction, average size and distribution), corrosion resistance and hydrogen permeation behaviors in the inter-critically reheated coarse-grained heat-affected zone (ICCGHAZ) of X80 pipeline steel. We observed that the M/A constituents’ characteristics mainly depend on the secondary peak temperature and cooling rates, while the microstructure style and prior austenite grain size are dependent on the first peak temperature. In addition, the variations in the M/A constituents’ characteristics result in different corrosion resistance and hydrogen permeation behaviors by changing the micro-galvanic effect and the number of hydrogen trapping sites. The high fraction and coarse grain size of M/A constituents are against the corrosion resistance and hydrogen permeation in ICCGHAZs, and their functional relationships are established. Moreover, the effects of the fraction of M/A constituents on the corrosion resistance and hydrogen permeation behaviors are much greater than those of the average size.

Mechanical properties and microstructure of graphene platelets reinforced Si3N4 composites have been investigated and compared to monolithic Si3N4. The microstructure shows that graphene platelets are parallel to each other and perpendicular to the hot pressing direction. Fracture toughness and flexural strength of composite with 1 wt.% graphene measured on polished surface perpendicular to hot pressing direction are 8.7 MPa·m1/2 and 892 MPa, respectively, which are increased about 14.5% and 20.2% compared with that parallel to hot pressing direction. The anisotropy of microstructure and mechanical properties of composites can be explained by the intrinsic anisotropy of graphene as well as the crack deflection energy release rate and the weak boundary bonding between graphene and Si3N4 caused by the thermal expansion mismatch.

Cutting heat conduction undergoes three stages that include intensity transient-state, transient-state, and steady-states. Especially during machining with coated cutting tools, in the conduction process, cutting heat needs to pass through a few micron thick coatings and then flow into the tool body. This heat conduction presents typical non-Fourier heat conduction characteristics. This paper focuses on the cutting temperature in transient heat conduction with a coated tool. A new analytical model to characterize the thermal shock based on the non-Fourier heat conduction was proposed. The distribution of cutting temperature in mono-layer coated tools during the machining was then illustrated. The cutting temperature distribution predicted by the Fourier heat conduction model was employed to compare with that by non-Fourier heat conduction in order to reveal the non-Fourier heat conduction effect in transient heat conduction. The results show that the transient heat conduction analytical model is more suitable for the intensity transient-state and transient-state in the process of cutting heat conduction.

In order to develop a new ceramic tool material with self-repairing capability, Al2O3/TiC/TiB2 ceramic tool material was prepared by vacuum hot-pressure sintering method. The toughening and strengthening mechanism of TiB2 on Al2O3/TiC substrate was analyzed. The results show that the ceramic tool material has good comprehensive mechanical properties when the TiB2 content is 10 vol.%. Its flexural strength was 701.32 MPa, hardness was 18.3 GPa, and fracture toughness was 6.2 MPa·m1/2, which were improved by 11.6%, 2.2% and 16.1% respectively, compared with the Al2O3/TiC tool material. Fracture surfaces of the Al2O3/TiC/TiB2 ceramic tool material were characterized by SEM, EDS and XRD. The results showed that the fracture mode was a mixture of transgranular fracture and intergranular fracture. The growth of Al2O3 and TiC grains can be effectively inhibited by adding appropriate amount of TiB2, and the internal grains of the material can be refined. The TiB2 has a uniform distribution in the matrix and acts as a diffusion toughening agent. The cutting performance of Al2O3/TiC/10 vol.%TiB2 tool material was further investigated. Experiments conducted on tools made of Al2O3/TiC and Al2O3/TiC/TiB2 materials showed that the main forms of wear for both tools were abrasive wear and bonded wear. The friction coefficient of Al2O3/TiC/TiB2 tools was reduced by 10.77% compared to Al2O3/TiC tools.

In this paper, the Voronoimosaic model and the cohesive element method were used to simulate crack propagation in the microstructure of alumina/graphene composite ceramic tool materials. The effects of graphene characteristic size and volume content on the crack propagation behavior of microstructure model of alumina/graphene composite ceramics under different interfacial bonding strength were studied. When the phase interface is weak, the average energy release rate is the highest as the short diameter of graphene is 10–50 nm and the long diameter is 1600–2000 nm. When the phase interface is strong, the average energy release rate is the highest as the short diameter of graphene is 50–100 nm and the long diameter is 800–1200 nm. When the volume content of graphene is 0.50 vol.%, the average energy release rate reaches the maximum. When the velocity load is 0.005 m s−1, the simulation result is convergent. It is proven that the simulation results are in good agreement with the experimental phenomena.

This study aimed at improving the cutting performance of a ceramic tool to which were added solid lubricant particles. We prepared the self-lubricating ceramic tool by adding CaF2@Al2O3 instead of CaF2, and the self-lubricating ceramic tool with Al2O3 as matrix phase, Ti(C,N) as reinforcement phase. The properties of the ceramic tool with different contents of CaF2@Al2O3 and CaF2 were studied by turning 40Cr. Compared with the ceramic tool with 10 vol.% CaF2, the main cutting force and the cutting temperature of the ceramic tool with 10 vol.% CaF2@Al2O3 decreased by 67.25% and 38.14% respectively. The wear resistance and machining surface quality of the ceramic tool with CaF2@Al2O3 were better than the ceramic tool to which were directly added CaF2. The optimal content of CaF2@Al2O3 particles was determined to be 10 vol.%. The addition of CaF2@Al2O3 particles effectively reduces the adverse effect of direct addition of CaF2 particles on the ceramic tool, and plays a role in improving the cutting performance of the ceramic tool.

The Al2O3/Ti(C,N) ceramic material added micron ZrO2 whisker and nano coated CaF2@Al(OH)3 powder was fabricated. The micron ZrO2 whisker was for the toughening and reinforcing phase and the nano coated CaF2@Al(OH)3 powder was the lubricant. For obtaining a ceramic material with optimal comprehensive mechanical properties and friction properties, the influences of different compositions of the ZrO2 whisker and nano coated CaF2@Al(OH)3 powder on the microstructure and mechanical properties were analyzed, respectively. The result demonstrated that as the addition of the ZrO2 whisker was 6 vol% and the addition of the nano coated CaF2@Al(OH)3 powder was 10 vol%, the optimal self-lubricating ceramic material had optimal mechanical properties. The hardness of the ceramic material was 16.72 GPa, the flexural strength was 520 MPa and the fracture toughness reached 7.16 MPa·m1/2. The formation of the intragranular structure, whisker toughening and the phase transition of ZrO2 were the main mechanisms.

By optimising the particle size of cladding alloy powders, in situ micron and submicron (Ti-V)C reinforced Fe-based laser cladding layers were prepared and the dry sliding friction properties were comparatively studied. Results showed that there were same phases of α-Fe, γ, TiC, and TiVC2 in the two cladding layers. The average grain size of the Fe-based matrix was 3.46 μm and 3.37 μm, the microhardness was 731 HV0.2 and 736 HV0.2, and the area ratio of carbides was 11.14% and 11.02%, respectively. The dry sliding wear resistance of the cladding layer reinforced by 1.95 μm carbides was 2.76 times higher than that of the 0.49 μm carbides. The failure mechanism of the cladding layer with the micron carbides was mainly caused by plastic deformation of the cladding layer matrix, whereas that of the submicron carbides involved both the plastic deformation of the cladding layer matrix and the abrasion that was caused by the peeled carbides.

The lubrication performance of graphene used as additive in 4-n-pentyl-4′-cyanobiphyl liquid crystal (5CB) for steel/steel contacts was studied on a ball-on-plate tribotester. The friction test results show that when the graphene content in the 5CB was 0.15 wt.%, and the lubricant and friction pairs were heated to 44⁻46 °C before friction tests, the lubrication performance of the 5CB was most improved. Compared with pure 5CB, 5CB+0.15 wt.% graphene suspension reduced the friction coefficient and wear scar diameter by up to 70.6% and 41.3%, respectively. The lubrication mechanisms have been tentatively proposed according to the test results. We speculate that the excellent lubrication performance of graphene/5CB suspensions may be attributed to the low shear resistance adsorption layer formed by graphene and 5CB molecules on the sliding surfaces. As the protective layer, it not only prevents direct contact between the rough sliding surfaces but also is easy to slide.