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Various contents of carbon fibers (CFs) and potassium titanate whiskers (PTWs) were added to an Fe-based impregnated diamond bit (IDB) matrix to enhance its adaptability to percussive–rotary drilling. A series of mechanical tests were conducted successively to find the effects of the reinforcing materials on the properties of the Fe-based IDB samples. Then, the fracture surfaces of the samples were analyzed via scanning electron microscopy (SEM) and energy-dispersive spectroscopy, and the worn surfaces and abrasive debris of the samples were analyzed using a laser scanning confocal microscope and SEM. The results show that both the CF and PTW can effectively improve the hardness and bending strength of an Fe-based IDB matrix, and those parameters reached their maximum values at the additive amount of 1 wt%. However, the CF had a better enhancement effect than the PTW. Furthermore, the CF improved the impact wear resistance of the IDB matrix, with a minimum wear rate of 2.38 g/min at the additive amount of 2 wt%. However, the PTW continuously weakened the impact wear resistance of the IDB matrix with increases in its content. Moreover, the morphologies of the worn surfaces indicated that the minimum roughness of the CF-reinforced IDB matrix decreased significantly to as low as 4.91 μm, which was 46.16% lower than that without CF, whereas the minimum roughness of the PTW-reinforced samples decreased by 11.31%. Meanwhile, the abrasive debris of the CF-reinforced samples was more uniform and continuous compared to that of the PTW-reinforced samples. Overall, the appropriate addition of CF or PTWs can enhance the mechanical properties of Fe-based IDB matrices, which can be used on different formations based on their impact wear resistance. [ABSTRACT FROM AUTHOR]

Resin-based friction materials (RBFM) are widely used in the fields of automobiles, agriculture machinery and engineering machinery, and they are vital for safe and stable operation. In this paper, polymer ether ketone (PEEK) fibers were added to RBFM to enhance its tribological properties. Specimens were fabricated by wet granulation and hot-pressing. The relationship between intelligent reinforcement PEEK fibers and tribological behaviors was investigated by a JF150F-II constant-speed tester according to GB/T 5763-2008, and the worn surface morphology was observed using an EVO-18 scanning electron microscope. The results showed that PEEK fibers can efficiently enhance the tribological properties of RBFM. A specimen with 6 ωt% PEEK fibers obtained the optimal tribological performance, the fade ratio was −6.2%, which was much higher than that of the specimen without the addition of PEEK fibers, the recovery ratio was 108.59% and the wear rate was the lowest, which was 1.497 × 10−7 cm3/(Nm)−1. The reason for the enhancing tribological performance was that, on the one hand, PEEK fibers have a high strength and modulus which can enhance the specimens at lower temperatures; on the other hand, molten PEEK at high temperatures can also promote the formation of secondary plateaus, which are beneficial for friction. The results in this paper can lay a foundation for future studies on intelligent RBFM. [ABSTRACT FROM AUTHOR]

In this study, poly (ether ether ketone) (PEEK)/polytetrafluoroethylene (PTFE) composites reinforced with carbon fibers (CFs) and graphite (Gr) were fabricated by compressive molding technology. The friction and wear properties of the PEEK/PTFE composites sliding against Si3N4 balls were investigated using ball-on-disk configuration under dry sliding conditions, and the morphologies of the worn surfaces were also observed with a scanning electron microscope (SEM) and a three-dimensional morphometer. The results indicated that the introduction of CFs significantly improved the tribological properties of the composites, but the friction coefficient of the PEEK/PTFE/CFs composites were higher than the pure PEEK/PTFE composites. However, it was found that a combinative addition of CFs and Gr creates an obvious synergetic effect of improving the friction-reducing and anti-wear abilities of the composites. The mechanisms of the improved tribological properties of the PEEK/PTFE/CFs/Gr composites were discussed based on the analysis of the worn surfaces and tribofilms. [ABSTRACT FROM AUTHOR]

The tribological performance of a glass fiber reinforced polyamide66 (GFRPA66) composite with varying fiber weight percentage (wt.%) [30 wt.% and 35 wt.%] is investigated in this study using a pin-on-disc tribometer. GFRPA66 composite specimens in the form of pins with varying percentages of fiber viz., 30 wt.% and 35 wt.% are fabricated by an injection molding process. Tribological performances, such as coefficient of friction (COF) and the specific wear rate (SWR), are investigated. The factors affecting the wear of GFRPA66 composites [with 30 wt.% and 35 wt.% reinforcements] are identified based on the process parameters such as load, sliding velocity, and sliding distance. Design Expert 13.0 software is used for the experimental data analysis, based on the design of experiments planned in accordance with the central composite design (CCD) of the response surface methodology (RSM) technique. The significance of the obtained results are analyzed using analysis of variance (ANOVA) techniques. To attain minimum SWR and COF, the wear performance is optimized in dry sliding conditions. The analysis of experimental data revealed that SWR and COF increased with increasing load, sliding velocity, and sliding distance for GFRPA66 [30 wt.%], but decreased with increasing polyamide weight percentage. The SWR for a maximum load of 80 N, and for a sliding velocity of 0.22 m/s, and a sliding distance of 3500 m for GFRPA66 composite specimens with 30 wt.% reinforcements are found to be 0.0121 m3/Nm, while the SWR for the same set of parameters for GFRPA66 composite specimens with 35 wt.% reinforcements are found to be 0.0102 m3/Nm. The COF for the GFRPA66 composite specimens with 30 wt.% reinforcements for the above set of parameters is found to be 0.37, while the GFRPA66 composite specimens with 35 wt.% reinforcements showed significant improvement in wear performance with a reduction in COF to 0.25. Finally, using a scanning electron microscope (SEM), the worn surfaces of the GFRPA66 are examined and interpreted. [ABSTRACT FROM AUTHOR]

In this study, aluminum alloy (Al7075) composites with a 4% weight fraction of tungsten carbide (WC) were manufactured using a stir casting process and the developed composites were subjected to various ageing temperatures. An attempt has been made to predict the age-hardening temperature with the enhanced mechanical and wear properties of Al7075-WC. The result shows that the composite specimen aged at 250 °C offered maximum tensile strength and the Brinell hardness number was increased by 37.1% and 50.5%, respectively; the maximum impact energy was observed to be 92.2% for the 450 °C aged composites, compared to the non-aged Al7075-WC composites. The strength properties of the Al7075-WC composite decreased to 30.86%, 4.7%, and 24.9% when the composite specimens aged at 350 °C. The mechanical properties of the Al7075-WC composite were increased at the age-hardening temperatures from 150 °C to 250 °C and decreased from 250 °C to 350 °C. The wear testing pin-on-disc setup utilized to determine the wear characteristics of the prepared MMC with wear parameters of load and sliding distance and the wear resistance of the composite specimens increased due to ageing. The fractography analysis of the composite samples carried out by scanning electron microscope (SEM) images revealed that the fracture of the composite during the tensile test is a mixture of ductile and brittle modes. [ABSTRACT FROM AUTHOR]

In the present study, electro-explosive spraying technology was used to prepare a multi-layer composite coating with a staggered spatial structure on a 45 steel substrate, and the mechanical properties and wear behavior of the coating were studied. The composite coating was prepared by spraying Mo as the bonding layer, then spraying high-carbon steel and aluminum bronze alternately as a functional coating. The cross-sectional morphology, surface morphology and the properties of the coating were analyzed with a scanning electron microscope (SEM), energy dispersive spectrometer (EDS), electron backscattered diffraction (EBSD) and a 3D profilometer. The bonding strength, friction and wear resistance of the coating were studied by the bonding strength experiment and by the friction and wear experiment. The results showed that it is feasible to prepare a composite coating with a sponge-like spatial structure with electro-explosive technology. There was metallurgical bonding as well as mechanical bonding between the adjacent coating layers. The composite coating had the advantages of uniform thickness, high compactness, high bonding strength and good wear resistance. [ABSTRACT FROM AUTHOR]

Magnesium alloys are attractive for the production of lightweight parts in modern automobile and aerospace industries due to their advanced properties. Their mechanical properties are usually enhanced by the incorporation with reinforcement particles. In the current study, reinforced AZ31 magnesium alloy was fabricated through the addition of bulk Al and the incorporation of SiC nanoparticles using a stir casting process to obtain AZ31-SiC nanocomposites. Scanning electron microscope (SEM) investigations revealed the formation of Mg17Al12 lamellar intermetallic structures and SiC clusters in the nanocomposites. Energy dispersive spectroscopy (EDS) detected the uniform distribution of SiC nanoparticles in the AZ31-SiC nanocomposites. Enhancements in hardness and yield strength (YS) were detected in the fabricated nanocomposites. This behavior was referred to a joint strengthening mechanisms which showed matrix-reinforcement coefficient of thermal expansion (CTE) and elastic modulus mismatches, Orowan strengthening, and load transfer mechanism. The mechanical properties and wear resistance were gradually increased with an increase in SiC content in the nanocomposite. The maximum values were obtained from nanocomposites containing 1 wt% of SiC (AZ31-1SiC). AZ31-1SiC nanocomposite YS and hardness were improved by 27% and 30%, respectively, compared to AZ31 alloy. This nanocomposite also exhibited the highest wear resistance; its wear mass loss and depth of the worn surface decreased by 26% and 15%, respectively, compared to AZ31 alloy. [ABSTRACT FROM AUTHOR]

The microstructural and wear properties of laser-cladding WC/Ni-based layer on Al–Si alloy were investigated by scanning electron microscope (SEM), X-ray diffraction (XRD), energy dispersive spectrometer (EDS) and wear-testing. The results show that, compared with the original specimen, the microhardness and wear resistance of the cladding layer on an Al–Si alloy were remarkably improved, wherein the microhardness of the layer achieved 1100 HV and the average friction coefficient of the layer was barely 0.14. The mainly contributor to such significant improvement was the generation of a WC/Ni-composite layer of Al–Si alloy during laser cladding. Two types of carbides, identified as M7C3 and M23C6, were found in the layer. The wear rate of the layer first increased and then decreased with the increase in load; when the load was 20 N, 60 N and 80 N, the wear rate of layer was1.89 × 10−3 mm3·m−1, 3.73 × 10−3 mm3·m−1 and 2.63 × 10−3 mm3·m−1, respectively, and the average friction coefficient (0.14) was the smallest when the load was 60 N. [ABSTRACT FROM AUTHOR]

AISI 304 has good physical and chemical properties and thus is widely used. However, due to the low thermal diffusivity, the cutting temperature of AISI 304 is high accelerating the wear of the tool. Therefore, tool wear is a major problem in machining hard cutting materials. In this study, we developed a new type of micro-groove tool whose rake surface was distributed with micro-groove by powder metallurgy based on the finite element temperature field morphology. We compared the wear of the proposed micro-groove tool with an untreated one by using a scanning electron microscope (SEM) and an X-ray energy spectrum. The abrasive, adhesive, and oxidation wear of the rake and the flank face of the micro-groove tool were lower than that of the untreated one. Due to the micro-groove on the rake face of the tool, the contact length between the tool and chip was reduced, leaving more extension space. Furthermore, chip extrusion deformation was avoided, and the energy caused by chip deformation was reduced. After 70 min of cutting, the counterpart reached the specified wear amount while the main cutting force, the feed resistance, and the cutting depth resistance of the proposed micro-groove tool were reduced by 16.1%, 33.9%, and 40.1%, respectively. With regard to steady state, the cutting temperature was reduced by 17.2% and the wear width of the flank face was reduced by 36.7%. [ABSTRACT FROM AUTHOR]

To investigate the relationship between surface microstructure and wear mechanism in D2/U71Mn wheel-rail material under different contact stress conditions, rolling wear tests using a GPM-40 wear machine to simulate the wheel-rail operation was performed. After wear tests, an optical microscope (OM), scanning electron microscope (SEM) and micro-hardness testers were used to characterize the microstructure and fatigue wear cracks. The results show that the thickness of the plastic deformation layer and surface hardness is increased with the increase of contact stress. Under high contact stress condition (1200 MPa), the severe plastic deformation layer led to the formation of fatigue wear of wheel-rail samples. Under a contact stress of 700 MPa, the wear mechanism of samples is adhesive wear and wear rate is low. With the increase of contact stress, the fatigue cracks are gradually severe. Under a contact stress of 1200 MPa, the wear mechanism of samples becomes fatigue wear and the fatigue wear cracks cause the increase of wear rate. The fatigue wear can accelerate the wear failure of wheel-rail samples. The fatigue wear cracks of wheel samples are severer than that of rail samples due to both the rate of plastic strain and the content of proeutectoid ferrite. [ABSTRACT FROM AUTHOR]