Tribological performance of iron- and nickel-base self-lubricating claddings containing metal sulfides at high temperature

Abstract

Iron-based coatings with the incorporation of solid lubricants have been prepared by means of laser cladding, in an effort to control friction and decrease tool wear at high temperatures during metal forming applications. The choice of a Fe-based powder has been considered advantageous, as it can lead to decreased costs compared to nickel-based claddings previously studied by the authors, in addition to having a lower environmental impact. In particular, the incorporation of transition metal dichalcogenides such as MoS2 as precursors leads to the encapsulation of silver in Fe-based self-lubricating claddings, resulting in a uniform distribution of the soft metal across the thickness of the coating. Subsequent tribological evaluation of the claddings at high temperatures shows that the addition of lubricious compounds leads to lower friction at room temperature and significantly decreased wear up to 600 °C compared to the unmodified iron-based reference alloy, although higher than similar self-lubricating Ni-based claddings. In order to cast light into these observed differences, the corresponding microstructures, phase composition, and self-lubricating mechanisms have been studied and compared for Fe- and Ni-based claddings having both of them the addition of silver and MoS2. The results suggest a key role of the formation of protective tribolayers on the counter body during high temperature sliding contact. Additional simulation of the phase evolution during solidification reveals that the formation of different chromium- and nickel-based metal sulfides in Fe- and Ni-claddings during laser cladding by the decomposition of MoS2 plays a key role in determining their tribological behaviour at high temperatures.

Effect of Cr on Microstructure and Properties of WVTaTiCrx Refractory High-Entropy Alloy Laser Cladding

“…Thereafter, they aroused great concern from researchers at home and abroad. Research has proved that RHEAs have excellent mechanical properties at high temperatures, even surpassing the widely used nickel-based alloy [2][3][4][5][6]. RHEAs, with excellent mechanical properties at elevated temperatures, are considered promising high-temperature application materials, which are suitable for complex working conditions such as atomic energy, aerospace, the military industry, advanced nuclear reactors, etc.…”

Improvement of the High Temperature Wear Resistance of Laser Cladding Nickel-Based Coating: A Review

“…However, as the temperature rose to 600 • C, the COF of the three sulfide-added coatings began to fluctuate sharply and the amount of wear increased greatly. This indicates that it is difficult for Ni 3 S 2 , CuS and Bi 2 S 3 to make an effective improvement in the abrasive resistance of Ni-based coatings at 600 • C. Sulfides are unstable and easily oxidized at high temperatures, particularly above 610 • C when the COF of the coating raises sharply, and are not effective in improving the high temperature wear resistance of nickel-based coatings [52]. The authors concluded that the encapsulation on the surface of sulfide by chemical plating proposed by Liu [53] can effectively inhibit its decomposition but also can boost the compatibility with the substrate.…”