Boride layer characterization and dry sliding wear behaviors of borided H13 steel at different durations and temperatures with nanoboron powder have been investigated. A single phase boride layer was ...formed at 800 °C and a double phase boride layer was obtained at 900 °C and 1000 °C. According to the boriding process with Ekabor II, higher ratio FeB/FeB + Fe2B and total boride layer were formed when nanoboron was used in the boriding process. It has been observed that the increment in the boriding temperature and boriding duration has increased the boride layer thickness from 6,34 μm to 103.26 μm. Manganese boride and chromium boride phases were determined along with iron borides in the boride layer. The hardnesses of borides formed on the H13 steel reached 2028 HV0.1 and the change in hardness from the surface to the interior was slower at samples which were borided at higher temperatures and durations. Fracture toughness was found to be in the range of 1.32–5.23 MPa-m1/2 depending on boronizing time in samples which were borided at 1000 °C. The increase in the boriding temperature and boriding duration led to increased wear resistance. At high temperature, microcrack-induced plastic deformation and fatigue; at room temperature, microcrack formation were dominant wear mechanisms.
•High temperature dry sliding wear behavior of borided H13 steel was evaluated.•The increase in the boride layer led to increased wear resistance.•The sample borided at 1000 °C for 6 h showed the best wear properties.•The hardnesses of borides formed on the H13 steel were reached to 2028 HV0.1.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
In this study, CoCrFeNiTi
0.5
Al
x
high-entropy alloys were produced by induction melting and their dry sliding wear behavior was examined at different temperatures. In addition to face-centered ...cubic (FCC) phases, low amounts of a tetragonal phase were detected in the microstructures of alloys without Al and microscratches were formed by wear particles on the worn surfaces of the alloy specimens. Two body-centered cubic (BCC) phases were detected in the alloy with 0.5Al and a fatigue-related extrusion wear mechanism was detected on the worn surface. The alloy specimen with a high Al content exhibited the best wear characteristics. No wear tracks were formed in single-phase BCC intermetallic alloys at room temperature and they exhibited a higher wear strength at high temperatures when compared to other samples.
Iron-based superalloys are alloys produced for use in corrosive environments as an alternative to high-cost nickel-based superalloys. However, their average strength and hardness, attributed to their ...austenitic structures, limit their use in tribological applications. In an attempt to counter these drawbacks, boriding was applied to an iron-based A286 superalloy having an initial surface hardness of 320 HV. Boriding kinetics, some mechanical properties, and tribo-wear (ambient air and 3.5 NaCl environment) behaviors of the formed boride layers were investigated. Multicomponent boride layers (consist of FeB, Fe2B, CrB, NiB, Ni4B3) were formed on the surface of the alloy, with hardness and thickness values of 1498–1961 HV and 20–130 μm, respectively, depending on the boriding temperature and the treatment time. The integral diffusion model was adopted to deal with the kinetics of monoboride and hemiboride layers formed on the surface. The boron activation energies of FeB, Fe2B, and DZ layer were estimated as equal to 175.86, 198.7, and 205.73 kJ mol−1, respectively. As a result of increased surface hardness, all of the borided samples displayed reduced friction coefficients and higher wear resistance compared to the untreated alloy, in both ambient air and 3.5% NaCl. However, the increase in wear resistance was not proportional to the increase in hardness; while the best wear resistance was obtained in samples borided at 850–950 °C for 6 h, the lowest wear resistance was obtained in samples borided for 4–6 h at 1050 °C. This situation was caused by the Kirkendall effect and residual stresses in the structure of alloying elements with different diffusion rates due to the high-temperature effect of the boriding process.
•Fe-based superalloy with average strengths and low hardness was successfully pack-borided.•Formed borides were examined using XRD, SEM-EDS, nanoindentation, microhardness, surface roughness and tribo-wear tests.•The hardness and elasticity modules of Fe-based superalloy were developed by boriding.•The friction and wear performance of A286 was improved with the boriding both in ambient air and 3.5% NaCl solutions.•Boriding open new possibilities for the use of Fe-based superalloys in tribo-corrosive environments.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Monel 400 was pack-borided in the temperature range of 1173–1273 K for exposure times of 2–6 h. The boride layers produced on the surface of the alloy were examined by scanning electron microscopy ...and phase identification was carried out by X-ray diffraction. The topmost layer on the borided Monel 400 was compact and contained the Ni
2
B phase while the diffusion zone contained grain boundary precipitates of borides. Boride layers of 35–290 µm thickness and 1002–1476 HV
0.025
hardness were obtained. SEM observations revealed a smooth interface between the boride layer and the diffusion zone. A kinetic model based on the integral method was applied to investigate the kinetics of Ni
2
B layer. The boron activation energy in the Ni
2
B layer was estimated as equal to 300.7 kJ mol
−1
. An experimental validation of the model was made by comparing the experimental layer thicknesses obtained, after boriding at 1198 K for 1 and 3 h, with predicted values.
Graphical Abstract
Full text
Available for:
EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
•A high entropy alloy with face-centered cubic structures was successfully boronized by nano-sized boronizing powders.•The microstructural and mechanical properties of the grown borides ...investigated.•The hardness and elasticity modules of FCC high entropy alloys with low surface hardness were developed by boronizing.•The friction and wear performance of the HEA was improved with the boronizing.•The wear environment had a significant effect on wear behavior.
High-entropy alloys (HEAs) with face-centered cubic (FCC) structures exhibit high toughness and corrosion resistance, but their average strengths and relatively low wear resistance can limit their engineering applications. In this study, FCC Al0.07Co1.26Cr1.80Fe1.42Mn1.35Ni1.10 HEAs were boronized for 4 h at temperatures of 900, 950, and 1000 °C to form hard, protective metal borides on their surfaces. The microstructural characteristics of the borides formed were examined using X-ray diffraction, scanning electron microscopy and energy-dispersive X-ray spectroscopy. The mechanical properties of the boride layers were studied by nanoindentation measurements, and the tribological performances of the layers were evaluated by ball-on-disk type wear tests in air, 3.5% NaCl and 5% H2SO4. Irrespective of the boronizing temperature, (Fe0.4Mn0.6)B, (Cr0.4Mn0.6)B, (CoFe)B2 and Cr2Ni3B6 phases were detected in the surfaces of the boronized samples. The surface hardnesses of the boronized samples reached nearly ten times the hardness of the as-cast HEA. The borides were effective in reducing friction as well as wear. Increasing the boronizing temperature increased the thicknesses of the coatings and further improved wear characteristics. Wear rates in 5% H2SO4 were generally higher than the wear rates in 3.5% NaCl, but the highest wear rates were observed in air.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This study is focused on a detailed investigation of high-temperature corrosion and oxidation behavior of borided CoCrFeNiAl0.5Nb0.5 HEAs, considering their use in advanced engineering applications. ...CoCrFeNiAl0.5Nb0.5 HEA was produced by arc melting. XRD and SEM-EDS analysis before boriding determined that the alloy consisted of four different phases with different chemical compositions. Powder-pack boriding of a CoCrFeNiAl0.5Nb0.5 HEA was performed at 1000 °C for 3 h in a boriding media containing 90 % boron carbide and 10 % sodium tetrafluoroborate. As a result of the boriding process, complex boride layers consisting of (CoFe)B2, CrFeB, CoNbB, FeB and NiB phases were obtained on the surface with a thickness of 40 μm and hardness of 3004 HV. it was determined that the microstructure with cauliflower appearance evolved towards a dense and non-porous appearance around 20 μm as the boron diffusing into the HEA microstructure filling the gaps of intermetallic compound in the single structure, HEA and borided HEAs were each subjected to a cyclic hot corrosion test at 900 °C in molten corrosion salts of Na2SO4 and V2O5. After hot corrosion tests, long rod-like structures were observed in both samples due to the excessive corrosion, while borided alloys were more resistant to hot corrosion damage. After oxidation tests, HEA consists of a compact protective alumina scale that provided better oxidation resistance, while non-protective mixed oxides with cracks were dominant in the borided HEA.
•Borided HEA's surface degradation properties were investigated at high temperature.•Boriding process enhanced the hot corrosion resistance of alloy.•The presence of B2 phases provided alumina scale as oxidation product in the alloy.•The boriding process weakened the oxidation resistance as it caused the aluminum to migrate deeper.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Waste utilization is an important alternative to reduce disposal costs, potential environmental pollution problems, decrement of natural resources and production costs. In this study, it is aimed to ...create a different usage area for the slag wastes that cause problems to the environment and factories. For this purpose, the usability of slags (blast furnace, ferrochromium and converter) as a reinforcement material in epoxy composites were investigated for tribological applications. Epoxy matrix composites were produced by adding 30% of reinforcements with 61 μm size. The epoxy composites were tested against a stationary Al2O3 ball in a ball-on-disk tester under the loads of 10, 15 and 20 N, at a sliding distance of 300 m and a rotational speed of 300 rpm. Wear mechanisms were also investigated by Scanning Electron Microscopy. Mostly, the slag fillers showed higher wear resistance than the Al2O3 reinforced composites. Among the slag fillers, the blast furnace exhibited superior tribological performance. While Al2O3 and blast furnace slag reinforced composites showed plastic deformation due to fatigue, transverse cracks and displaced reinforcement particles were observed in ferrochromium slag and converter slag reinforced composites. Increasing the applied load caused acceleration in wear rate. Thermal conductivity was increased by particle addition, which contributed to the improvement of the wear performance. This study provided that industrial wastes can be used as reinforcement material in composites and thus a cleaner environment can be obtained.
•The usability of slag as a reinforcement in epoxy composites is investigated.•Use of blast furnace, ferrochromium and converter slags are compared with Al2O3.•Slag reinforcement offers better wear resistance compared to Al2O3.•The type of reinforcement significantly affects the wear behavior.•Use of industrial waste in the composite reduces its environmental impact.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Ti–TiAl3 in-situ composites containing different percentages of Nb and B were effectively produced from Ti, Al, Nb and B powders by electric current assisted sintering (ECAS) technique which is a ...powder metallurgy processing method. Samples are sintered for 90 s with 2000 A current. The effect of B and Nb on the hardness, fracture toughness and wear resistance of samples were studied. The microstructure properties of the sintered samples were analysed with scanning electron microscopes (SEM), the phases in the samples were determined with XRD and their hardness and fracture toughness values were measured with a Vickers hardness tester with a load of 0.98 N and 98 N respectively. The highest fracture toughness value has been obtained with wt %10 Nb addition as 5.23 MPa m1/2, whereas the highest hardness was determined as 965 HV for wt%5 B reinforced in situ-Ti-TiAl3 composite. Best wear resistance was obtained in the 47.5Ti-47.5Al–5B sample. While Nb additive had a negatory effect on wear resistance, additive B had a positive effect on wear resistance.
•TiAl intermetallics reinfoced with Nb and B, successfully produced by Electric Current Activated (Assisted) Sintering (ECAS) process at very short times (90 s).•The highest value obtained in fracture toughness was 5.23 MPa m1/2.•While Nb additive had a negatory effect on wear resistance, additive B had a positive effect on wear resistance also into hardness.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In the present study, the surface of AISI H13 hot-work tool steel was borided with EKabor II powders using powder pack-boriding method. The process was carried out at 800, 900 and 1000°C temperatures ...for 2, 4 and 6h periods. The wear tests were carried out using a ball-on disc tribometer at room temperature and 500°C on borided and untreated AISI H13 hot-work tool steel. Scanning electron microscope (SEM), optical microscope, 3D profilometer, X-ray diffraction analysis and micro-hardness tester were used in the evaluation of micro-structure and wear data. The increase in the boriding temperature and boriding period led to increased thickness and hardness of the boride layer. Boriding at 800°C resulted with formation of Fe2B, Mn2B, Cr5B3, phases, while FeB, Fe2B, Mn2B, and Cr5B3 boride phases occurred at 900 and 1000°C. Dominant wear mechanisms were microcrack-induced plastic deformation during high temperature wear tests; oxidation and microcrack formation during room temperature wear tests; and oxidation and severe plastic deformation for the untreated specimen.
•Boriding process was performed on AISI H13 steel by powder pack boriding.•Friction coefficients and wear mechanisms at room and 500°C were investigated.•Boriding was effective on the change of wear mechanism of the AISI H13.•Friction coefficient and volume loss values were higher at high temperature.•Wear mechanisms occurred depending on hardness and phase structures of AISI H13.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Boronizing processes were carried out at 900 °C, 950 °C and 1000 °C for 2, 4 and 6 h to improve the wear performance of Monel 400 alloy. According to microstructure analyses and nanoindentation ...tests, Ni2B, FeNiB and FeB phases were detected as dominant phases in the boronized layer. Apart from this, it was observed that the amount of Cu deposits in the boronized layers increased depending on the increasing boronizing temperature. After the boronizing process, the boride layer thickness and hardness values were found to be in the range of 32–272 μm and 12.76–17.83 GPa, respectively. From the results of dry sliding wear test, the wear volume loss values of the boronized Monel 400 alloy decreased by approximately 25 times compared to the untreated samples. The lowest volume loss value among all test samples was observed in the boronized sample at 950 °C for 4 h. In addition to the hardness value, it was determined that the morphology and mechanical properties of the boronized layer were also effective on the wear results. Plastic deformation, delamination and oxidation type wear mechanisms were observed as the dominant wear mechanisms in the room and high temperature tests of boronized samples.
•Ni2B, FeNiB and FeB phases were detected and hardness increased up to 10×.•The boronized layer thickness and hardness were 32–272 μm and 12.76–17.83 GPa.•Boronizing provided to have higher wear resistance under both RT and HT conditions.•Cu islets formed in high temperature boronizing affected the wear negatively.•A decrease in wear loss was observed due to the increase in the hf/hmax ratio.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
PDF
