Three-body abrasive wear of 0.2 wt%-C martensitic steel was conducted in a dry-sand rubber wheel test apparatus following non-standard G65-16 test procedure. The specific wear rate (SWR) of the ...experimental alloy was compared against other microstructures of equivalent hardness. It was observed that the SWR of the experimental alloy follows the Type-1 category, in which hardness plays a major role in controlling wear. The wear mechanism was found to be predominantly micro-cutting followed by furrow and pitting. The deformation of microstructure along the depth from the wear surface was studied by Focused Ion Beam(FIB) milling-Transmission Electron Microscopy(TEM) and X-ray diffraction (XRD), following conventional and modified Williamson-Hall and Warren-Averbach analysis. The crystallographic study reveals limited plastic deformation of martensite (α′) within a shallow depth from the worn surface, as indicated by marginal change in the character and density of dislocation, which results in higher SWR owing to the inablility of the α′-phase to accommodate the strain energy of abrasion.
In this study, authors reinforced micro (0–10 wt%)- and nano (0.8–1.8 wt%)-Al
2
O
3
particles into the AA7075 matrix to enhance wear resistance. Comprehensive microstructural analysis, including ...optical microscopy, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy, confirmed the development of robust intermetallic compounds and uniform distribution of reinforcements. Using XRD analysis, peak detection of the Al
2
O
3
and MgZn
2
was observed. Al, Al
2
CuMg, and Al
8
Fe
2
Si were identified as the primary phases, and monolithic and composite materials both showed minor MgAl
2
O
4
formation. Ball-on-flat tests (5 and 10 N loads) assessed wear and friction behaviors. Potentiodynamic polarization tests were employed to examine the corrosion behavior of both the monolithic alloy and the manufactured composites. The composite with 1.8 wt% nano-Al
2
O
3
at a 5 N load demonstrated a 53% lower wear rate and 16% reduced friction. Predominant wear mechanisms included abrasive, oxidative, adhesive, and delamination. Corrosion test findings indicated that the composite containing (0.8 wt% nano-alumina and 5 wt% micro-alumina) exhibited superior corrosion resistance compared to the monolithic alloy and other composites.
Joining of high strength materials using friction stir welding (FSW) is difficult due to severe tool wear and change in the shape/size of the tool. However, quantitative understanding of tool wear ...during FSW of high melting point metallic materials is very limited. Here we present quantitative wear analysis of H13 steel tool during FSW of CuCrZr alloy. Higher amount of total tool wear is observed for faster tool rotational speeds, and slower traverse speeds. Progressive wear rate shows similar relationship with these process parameters during initial traverse stage. With further tool traverse the wear rate decreases significantly and is not much affected by the process parameters. The quantitative wear study provides insights about tool wear during FSW process and would be useful to better estimate and improve tool life. This would also be helpful to optimize the process parameters and tool shape to reduce tool wear during FSW of high strength materials.
•Higher tool RPM leads to greater tool wear due to enhanced surface velocities.•Tool wear decreases with increase in traverse speed due to reduced interaction time.•Progressive wear rate is highest during first 300mm of tool traverse.•Wear rate decreases as tool approaches a self-optimized shape after long traverse.•Effect of process parameters on wear rate is significant only during initial stage.
Titanium alloy TB6 is often used to produce key load carrying parts in the aviation and aerospace industries. The superior mechanical properties pose challenges to machining processes, bringing about ...such problems as rapid tool wear. In this paper, fine-grain WC/Co tools were utilized in dry turning of the TB6 alloy. The wear modes and wear mechanisms of the cutting tools at different cutting speeds were detailed. The analysis showed that the wear on the tool rake face was characterized as crater formation. The principal wear mode observed on the tool flank face appeared to be microchipping near the region of the cutting edge. The adhesion was more pronounced on the rake face than on the flank face. The clusters of WC particles were pulled out from the Co binder along the grain boundaries, which led to adhesive wear and left an intergranular fractured surface. The crater wear was a result of the elements of the cutting tool diffusing into the adhering material, which was carried away by the flowing chip, leading to a transgranular dissolution of the WC particles, and the worn surface was smooth. The chemical reaction possibly took place at the tool/adhering material interface, where the newly formed compounds were carried away by the flowing chip. The hard particles that adhered to the back surface of the titanium chip probably abrade the tool surface, causing abrasive wear.
In this study, a new processing technique, friction stir processing (FSP) was used to incorporate SiC and MoS2 particles into the matrix of an A356 Al alloy to form surface hybrid composite. The tool ...rotation rate was changed from 630 to 1600rpm and a tool tilt angle of 3° was applied. Higher tool rotation rate was found to causes a more uniform dispersion of reinforcing particles and thus, decreases particles clustering. Dry sliding wear tests were conducted using a pin-on-disc machine. The subsurface deformation was assessed as a measure of variation in microhardness along the depth normal to the cross-section of the worn surface. It was found that the wear resistance of the processed samples improved significantly as compared to that of the as-cast alloy. Microstructural analysis showed that a MoS2 rich layer on the top of worn surface helped to decrease the plastic deformation in subsurface region and alleviate severe wear. The improvement in wear resistance of surface hybrid composite compared to that of the as-cast alloy was found to be more pronounced under higher applied loads.
Wear resistance of ZrB2 based ceramic composites Medveď, Dávid; Balko, Ján; Sedlák, Richard ...
International journal of refractory metals & hard materials,
June 2019, 2019-06-00, 20190601, Volume:
81
Journal Article
Peer reviewed
The wear resistance and tribological characteristics of spark plasma sintered ZrB2 + B4C, ZrB2 + SiC and ZrB2 + ZrC composites were investigated under dry sliding conditions at applied loads of 5 N ...and 50 N in air. The microstructure, deformation and damage characteristics were studied using scanning electron microscopy, confocal electron microscopy, a focused ion beam and atomic force microscopy. The friction coefficient values were very similar for all composites with values ranging from 0.63 to 0.72 and with the lowest value recorded for the ZrB2 + SiC composite at a 5 N applied load. The ZrB2 + ZrC composite was the most wear resistant, with wear rates at a 5 N load of 6.15 × 10−6 mm3/(N·m) and at a 50 N of 7.3 × 10−6 mm3/(N·m). None, or a very limited number of grain pull-outs and/or lateral fractures of grains were found during the wear tests. At the 5 N load, abrasive grooves connected with deformations and Hertzian crack formations were the main wear mechanisms in all systems, with limited crack formations in the ZrB2 + ZrC composite. Tribofilm formations connected with debris origin, oxidation and tribochemical reactions were dominant in all composites, with similar chemical compositions but different sizes and thicknesses at the 50 N load.
•To enhance the oxidation resistance, COF, WR and KIC different additives (SiC, B4C and ZrC) have been introduced to ZrB2.•Detailed understanding of the tribological characteristics of Zirconium Diboride composites.•Description and understanding of tribochemical reactions.
In this work, the high strength AA7050 Al–Zn–Mg alloys were successfully processed by 1, 2, 3, 4, 5, and 6 passes Equal-channel Angular Pressing (ECAP) at room temperature. Alloys' growing strength ...is achieved after the increased ECAP passes. Besides, the combined effect of ultra-fine grains (UFG) with the average size of 46 nm, high dislocation density, and numerous nanoparticle precipitation contributed to the ultra-high strength in 6 passes aluminum ECAPed alloy. After the dry sliding wear testing, the microstructure refinement and improvement of strength lead to this transformation of the wear mechanism after ECAP passes. Furthermore, the linear relationship between strength and wear rate is observed in this investigated Al–Zn–Mg alloy, which is helpful to predict the corresponding wear rate and strength.
•Ultra-high strength AA7050 Al–Zn–Mg alloy with UTS value of 704.8 MPa is obtained via six ECAP passes at room temperature.•The ultra-fine grains (UFG), high dislocation density, and numerous nanoparticles contributed to the ultra-high strength.•The wear mechanisms transform from adhesive, delamination, and ploughing bands to abrasive as the increased ECAP passes.•The linear relationship between strength and wear rate is observed in this investigated Al–Zn–Mg alloy.
The work investigates the effect of corundum (Al2O3) reinforcement on the dry sliding wear of LM30 aluminium alloy composites. Composites with the different size range of corundum particles (fine; ...1–20 μm, medium; 32–50 μm and coarse; 75–106 μm) and weight percentages varying from 5 to 20 wt% were prepared. The stir casting process was used for the fabrication of composites. LM30 billets were melted at 850 and stirred with the graphite stirrer for 3–4 min. Corundum particles were added to the melt and the molten mass was stirred for another 3–4 min. Finally, the mixture was poured into a cast iron mould. Pins of 8 mm diameter were prepared for wear test and tested against the hardened die steel disc. Optical microscopy of the composites revealed a uniform distribution of corundum particles in the matrix. The microstructure of the composite also got refined. The acicular morphology of eutectic silicon in base alloy got refined to globular for the composites leading to improvement in the hardness of the composites. Dry sliding wear analysis of the composites revealed the decrement in the wear rate of the composites over the base alloy. Similar to the wear rate, the coefficient of friction of the composites also decreased with the increase in the corundum weight percentage. Finally, the wear tracks and debris analysis of the composites revealed the underlying wear mechanisms during the dry sliding wear behavior at a low contact pressure of 0.2 MPa and high contact pressure of 1.8 MPa. The wear mechanism of the composite is dependent on contact pressure. At low contact pressure of 0.2 MPa, the abrasive type wear transformed to adhesive type at a high contact pressure of 1.8 MPa.
•Corundum particle reinforced composites provided a superior wear resistance.•Abrasive and adhesive wear mechanisms were dominant at low and high contact pressures, respectively.•Cross-section study revealed the formation of tribolayer and plastically deformed layer.
During metal cutting with the textured tools, a variable local friction exists due to differences in the contact behavior owing to the presence of microtextures. The available periodic or aperiodic ...microscopic hierarchy on the textured tool surface changes the tribological characteristics and metal cutting performances. The friction and wear characteristics are difficult to ascertain in the metal cutting tests as the chips continuously slide over the tool rake face under dynamic wear conditions. The present study is conducted to closely predict the frictional coefficient and wear mechanisms for textured carbide cutting tools using an open tribometer. Tests have been performed to evaluate the tribological performance of hard coatings deposited by physical vapor deposition (PVD) method on laser textured WC/Co surfaces. PVD AlTiN and AlCrN coated plain and microhole textured WC/Co pins were tested against rotating Ti6Al4V counterpart to predict the extreme pressure tribological behavior. The results were evaluated in terms of the coefficient of friction, wear mechanisms, coating degradation behavior and surface damages. Coating and texturing on the carbide pins reduced the friction by 27% compared to uncoated plain carbide pins.
•Friction and wear studies for textured WC/Co have been successfully mimicked using open tribometer.•Coated textured WC/Co could reduce friction by ~27%.•Microtextures act as microcutting zones causing periodic adhesion and localized ridge formation.•Binder depletion, severe abrasion and TiC formation were detected underneath the transfer layers on textured carbide pins.
AlCoCrCuFeNi high entropy alloy particles were laser surface alloyed on Ti–6Al–4V substrate to improve the tribological properties. The microstructure, phase formation and hardness improvement of the ...laser alloyed surface were examined. The wear resistance of the laser alloyed specimen were evaluated through pin-on-disc apparatus and compared with substrate specimen. The wear mechanism of the worn-out surface and roughness were studied. The laser alloyed specimen exhibits dual solid solution along with the BCC phase. The alloyed region shows dendrite and interdendrite structure with equiaxed grain formation. The hardness of laser alloyed region is 3 times higher than the substrate material due to dominant BCC phase formation. The laser alloyed specimen shows higher wear resistance compared to substrate due to solid solution strengthening and intermetallic formation. The wear resistance of the laser alloyed specimen was 2.62 times than the substrate at 50 N load and 0.9 m/s sliding velocity. Abrasive, adhesive wear and severe plastic deformation were observed in the substrate specimen, whereas in the laser alloyed specimen mild abrasive wear was observed. The laser alloyed specimen has 0.56 times the coefficient of friction of the Ti–6Al–4V substrate at 50 N load and 0.9 m/s sliding velocity due to self-lubrication property of HEA elements. Surface roughness of worn-out laser alloyed specimen was 0.44 times that of the Ti–6Al–4V substrate.
Graphic Abstract
