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During the electrical discharge machining (EDM) process, the tool electrode wear is inevitable, which affects the process precision of the micro-hole. In the present experimental investigation, a fixed reference axial compensation (FRAC) method is proposed to enhance the machining precision of micro-hole. The effect of pulse power, compensation methods, and electrode materials on the depth and roundness factor of micro-hole are explored. The experiment results show that the FRAC method can realize the accurate compensation and reach the expected depth hole processing. When the FRAC is used, the depth deviation is less than 0.43%, and the minimum difference from the expected depth is only 0.106 µm. In addition, the micro-holes of tungsten steel and brass electrodes machine by the FRAC method were close to the expected depth, the difference from the expected depth less than 0.7%, but the bottom of micro-hole produced a cone. However, compared to tungsten steel and brass electrodes, the copper electrode has a better processing performance, the roundness factor is up to 79.8%. When the long-pulse power supply is applied, the expected depth of 400–1,600 µm blind holes with a better processing shape, and the phenomenon of the cone at the bottom are not apparent. Therefore, the proposed FRAC method can be utilized in many high-end manufacturing fields to improve the precision of the micro-hole for micro features.

In this study, plasma‐sprayed Al2O3–Cr2O3 coatings with different contents of graphene nanosheets were prepared for investigating effects of the graphene on microstructure, mechanical properties, and wear behavior of the coating. The experimental results showed that graphene increased the porosity and the microhardness of the coating. But excessive graphene decreased the microhardness remarkably. Besides, the anti‐crack initiation and propagation abilities of the coatings with graphene improved significantly. The wear rate of the coatings decreased first, and then increased with increasing the graphene content. Impressively, the wear rates of the coating with 2.9% graphene decreased by 33.5% and 36.7%, compared with those of the coating without graphene under normal loads of 5 and 15 N, respectively. The main wear mechanisms of the coatings with and without graphene are brittle fracture and abrasive wear. [ABSTRACT FROM AUTHOR]

In this paper, nanostructured Al2O3-40%YSZ (AZ) and nano-MoS2/Al2O3–40%YSZ (AZM) powders and coatings are prepared and studied to reveal the effect of nano-MoS2 on the friction and wear behavior of the coating. The morphology, surface roughness and hardness are observed and measured by a scanning electron microscope, a laser scanning confocal microscope and a micro-hardness tester. The ability to resist fracture of the coatings is evaluated by scratch tests. The friction and wear tests of the coatings are conducted by a ball-on-disc tribometer. The experimental results show that AZ and AZM coatings have similar morphology and roughness. But nano-MoS2 decreases the hardness and improves the ability to resist fracture of the coating. Besides, nano-MoS2 decreases the coefficients of friction of the coating when the normal loads are high. The wear rates of AZM coating decrease by 38.7%, 29.7%, 23.6% and 11% compared with those of AZ coating under normal loads of 5N, 10N, 15N and 20N. The addition of nano-MoS2 endows the coating self-lubricating function. The main wear mechanism of the coatings is micro-fracture accompanied by splat delamination and slight abrasion wear. [ABSTRACT FROM AUTHOR]

In this paper, nanostructured Al2O3-40%YSZ (AZ) and nano-MoS2/Al2O3–40%YSZ (AZM) powders and coatings are prepared and studied to reveal the effect of nano-MoS2 on the friction and wear behavior of the coating. The morphology, surface roughness and hardness are observed and measured by a scanning electron microscope, a laser scanning confocal microscope and a micro-hardness tester. The ability to resist fracture of the coatings is evaluated by scratch tests. The friction and wear tests of the coatings are conducted by a ball-on-disc tribometer. The experimental results show that AZ and AZM coatings have similar morphology and roughness. But nano-MoS2 decreases the hardness and improves the ability to resist fracture of the coating. Besides, nano-MoS2 decreases the coefficients of friction of the coating when the normal loads are high. The wear rates of AZM coating decrease by 38.7%, 29.7%, 23.6% and 11% compared with those of AZ coating under normal loads of 5N, 10N, 15N and 20N. The addition of nano-MoS2 endows the coating self-lubricating function. The main wear mechanism of the coatings is micro-fracture accompanied by splat delamination and slight abrasion wear. [ABSTRACT FROM AUTHOR]

Fe–Cr–B hardfacing alloys with different nano-additives content were investigated. The effects of nano-additives on the microstructures of hardfacing alloy were studied by using optical microscope, scanning electron microscope, X-ray diffractometer. The hardness and the fracture toughness of hardfacing alloys were measured, respectively. The sliding wear tests were carried out using a ball-on-disc tribometer. The experimental results showed that primary carbide of hardfacing alloys was refined and its distribution became uniform with content of nano-additives increased. The hardfacing alloys are composed of Cr 7 C 3 , Fe 7 C 3 , α-Fe and Fe 2 B according to the results of X-ray diffraction. The hardness of hardfacing alloys increased linearly with the increase of nano-additives. The hardness of the hardfacing alloy with 1.5 wt.% nano-additives increased 54.8% than that of the hardfacing alloy without nano-additives and reached to 1011HV. The K IC of the hardfacing alloy with 0.65 wt.% nano-additives was 15.4 MPam 1/2 , which reached a maximum. The value increased 57.1% than that of the hardfacing alloy without nano-additives. The wear rates of the hardfacing layer with 0.65 wt.% and 1.0 wt.% nano-additives decreased about 88% than that of the hardfacing layer without nano-additives. The main wear mechanism was adhesion wear. [ABSTRACT FROM AUTHOR]