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Browsing by Author "Rajput, S.S."

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  • High-temperature tribological behaviour and machining performance of self-lubricant CrAlNAg coatings for dry milling operations
    Publication . Rajput, S.S.; Upadhyay, C.; Gangopadhyay, S.; Fernandes, F.; Fernandes, Filipe
    Tribological and machining performance of CrAlNAg coatings having different Ag content tested against AISI 1045 medium carbon steel were assessed. Wear track was evaluated by scanning electron microscopy and energy dispersive spectroscopy. 3D topography of wear track and ball counterpart was determined by non-contact type profilometer. The formation of different oxide phases on track was confirmed using Raman spectroscopy. CrAlNAg9 and CrAlNAg12 coatings were found beneficial in reducing material adhesion from counterpart thus providing protective layers to counterpart, whereas small addition of Ag did not provide any improvement on CrAlN coating performance. CrAlNAg9 coated milling inserts demonstrated best results in terms of reduction in chip temperature (∼17.5 %), cutting forces, surface roughness (∼47 %) and chip thickness (∼12.7 %) compared to uncoated inserts.
    2024Journal article Open access Show more
  • Room and high temperature tribological performance of CrAlN(Ag) coatings: The influence of Ag additions
    Publication . Rajput, S.S.; Gangopadhyay, S.; Yaqub, T.B.; Cavaleiro, A.; Fernandes, Filipe
    The present study aims to investigate the effect of the addition of Ag on the tribological performance of a CrAlN coating system, at room and high temperatures (600 °C). The addition of Ag, in general, has been seen beneficial in lowering the coefficient of friction (COF) at room and high temperatures. Independent of the decrease of COF with Ag additions, the specific wear rate was degraded. The only exception was the CrAlNAg9 coating with 8.6 at.% of Ag which exhibited the lowest specific rate at room temperature while maintaining its comparable wear resistance properties with that of reference CrAlN coating at 600 °C. The CrAlNAg9 coating also demonstrated coefficient of friction (COF) of 0.16 and 0.26 at room temperature and 600 °C, respectively. Formation of Ag and AgCrO2-rich tribolayer during sliding at high temperature was responsible for lubricious properties of CrAlN(Ag) coatings. However, doping the coatings with small content of Ag (around 2.4 at.%) was not effective in decreasing the COF, nor the specific wear rate under high temperatures. On the other hand, high concentration of Ag (11.8 at.% and above) had a detrimental influence on mechanical properties and poor resistance to oxidation at elevated temperature compromising both friction and wear properties of the CrAlNAg12 and CrAlNAg16 coatings.
    2022Journal article Unknown Show more