A comparative study on the microstructure and surface property evaluation of coatings produced from nanostructured and conventional WC–Co powders HVOF-sprayed on Al7075

Lekatou, A.; Sioulas, D.; Karantzalis, A. E.; Grimanelis, D.

doi:10.1016/j.surfcoat.2015.06.017

Cited by 74 publications

(40 citation statements)

References 109 publications

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“…Moreover, the fluctuation of the friction coefficient and the running-in period both decreased in duration with the increasing temperature, probably due to the lower initial resistance to the conformation between the two sliding surfaces as a result of the formation of larger amounts of the oxide films with lubricating properties at higher temperatures. This also suggests that there was a more efficient activation of wear protection processes at higher temperatures, which can be attributed to the more uniform distribution of the lubricating oxides over the wear track and the more active sites for oxidation induced by the larger fraction of interphase boundaries [40]. The average values for the friction coefficient during the steady period, R a , of the worn surfaces and the wear rate are presented in Table 1.…”

Section: Friction and Wear Propertiesmentioning

confidence: 96%

Improvement in Tribological Properties of Cr12MoV Cold Work Die Steel by HVOF Sprayed WC-CoCr Cermet Coatings

Hong

Wang

et al. 2019

Coatings

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The main objective of this study was to develop an efficient coating to increase the wear resistance of cold work die steel at different temperatures. The microstructures of high-velocity oxygen-fuel (HVOF)-sprayed WC-CoCr coatings were evaluated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The effect of temperature on the tribological properties of the coatings and the reference Cr12MoV cold work die steel were both investigated by SEM, environmental scanning electron microscopy (ESEM), X-ray diffraction (XRD), and a pin-on-disk high-temperature tribometer. The coating exhibited a significantly lower wear rate and superior resistance against sliding wear as compared to the die steel at each test temperature, whereas no major differences in terms of the variation tendency of the friction coefficient as a function of temperature were observed in both the coatings and the die steels. These can be attributed to the presence of nanocrystalline grains and the fcc-Co phase in the coating. Moreover, the wear mechanisms of the coatings and the die steels were compared and discussed. The coating presented herein provided a competitive approach to improve the sliding wear performance of cold work die steel.

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Section: Friction and Wear Propertiesmentioning

confidence: 96%

Improvement in Tribological Properties of Cr12MoV Cold Work Die Steel by HVOF Sprayed WC-CoCr Cermet Coatings

Hong

Wang

et al. 2019

Coatings

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“…A standard three electrode cell (with Ag/AgCl as the reference electrode and a platinum gauze as the counter electrode) was R connected to the Gill AC potensiostat/galvanostat by ACM Instruments. The corrosion current densities were determined by Tafel extrapolation, by conforming to several criteria analytically documented in previous efforts [36,37]. Reverse (or cyclic) polarization at a scan rate of 10 mV/min was carried out to evaluate the susceptibility of the rebars to localized corrosion.…”

Section: Electrochemical Testingmentioning

confidence: 99%

“…A negative hysteresis loop (i.e. a loop formed by anodic reverse scans corresponding to higher current densities than the current densities of the forward scans) signifies occurrence of localized corrosion [37]. Two types of electrolyte were used: a) The first electrolyte contained (1.8-1.8x/100) g of agglomerates of Ca(OH) 2 per l of an AR mimicking solution (pH=3.1).…”

Section: Electrochemical Testingmentioning

confidence: 99%

Effect of fly ash on the corrosion performance and structural integrity of stainless steel concrete rebars in acid rain and saline environments

Lekatou

Tsouli

Nikolaidis

et al. 2019

Frattura Ed Integrità Strutturale

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The corrosion behavior of 304L stainless steel rebars in an alkaline solution simulating new concrete subjected to acid rain attack and a mildly to slightly acidic solution simulating corroded cover concrete that exposed the reinforcement to direct acid rain attack, was investigated by reverse polarization. Both solutions contained Ca(OH)2 and fly ash (0-25 wt.% of the dry mixture). Concrete cubes containing 0-25 wt.% fly ash and reinforced with 304L rebars were subjected to salt spraying for 4 m. Although the polarization behaviors in the two electrolytes were different, the relative trends with respect to the fly ash contents were similar. The beneficial effect of fly ash (up to 20 wt.%) on the corrosion resistance of 304L rebars was demonstrated. However, a deteriorating effect was realized at 25 wt.% addition. Partial replacement of cement by fly ash did not significantly affect the tensile properties of the 304L rebar before or after 4 m of salt spraying. The elastic modulus and percent elongation presented a slight decrease after 4 m of salt spraying, irrespectively of FA content. Corrosion-wise, 304L can replace 316L stainless steel provided that FA has been added to the concrete mixture, even at low contents (10 or 15 wt.%).

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“…The main concept of this technique is that pitting would occur if the current density of the anodic portion of the return scan is higher than the current density of the forward scan for the same anodic potential [41]. This type of hysteresis is labelled as "negative hysteresis" (More details can be found in [42]). …”

Section: Corrosion Testingmentioning

confidence: 99%

Al-Co Alloys Prepared by Vacuum Arc Melting: Correlating Microstructure Evolution and Aqueous Corrosion Behavior with Co Content

Lekatou

Sfikas

Petsa

et al. 2016

Metals

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Hypereutectic Al-Co alloys of various Co contents (7-20 weight % (wt.%) Co) were prepared by vacuum arc melting, aiming at investigating the influence of the cobalt content on the microstructure and corrosion behavior. Quite uniform and directional microstructures were attained. The obtained microstructures depended on the Co content, ranging from fully eutectic growth (7 wt.% and 10 wt.% Co) to coarse primary Al 9 Co 2 predominance (20 wt.% Co). Co dissolution in Al far exceeded the negligible equilibrium solubility of Co in Al; however, it was hardly uniform. By increasing the cobalt content, the fraction and coarseness of Al 9 Co 2 , the content of Co dissolved in the Al matrix, and the hardness and porosity of the alloy increased. All alloys exhibited similar corrosion behavior in 3.5 wt.% NaCl with high resistance to localized corrosion. Al-7 wt.% Co showed slightly superior corrosion resistance than the other compositions in terms of relatively low corrosion rate, relatively low passivation current density and scarcity of stress corrosion cracking indications. All Al-Co compositions demonstrated substantially higher resistance to localized corrosion than commercially pure Al produced by casting, cold rolling and arc melting. A corrosion mechanism was formulated. Surface films were identified.

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A comparative study on the microstructure and surface property evaluation of coatings produced from nanostructured and conventional WC–Co powders HVOF-sprayed on Al7075

Cited by 74 publications

References 109 publications

Improvement in Tribological Properties of Cr12MoV Cold Work Die Steel by HVOF Sprayed WC-CoCr Cermet Coatings

Improvement in Tribological Properties of Cr12MoV Cold Work Die Steel by HVOF Sprayed WC-CoCr Cermet Coatings

Effect of fly ash on the corrosion performance and structural integrity of stainless steel concrete rebars in acid rain and saline environments

Al-Co Alloys Prepared by Vacuum Arc Melting: Correlating Microstructure Evolution and Aqueous Corrosion Behavior with Co Content

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