Temperature-induced wear micro-mechanism transition in additively deposited nickel alloys with different solid lubricants.

Additive manufacturing of self-lubricating alloys plays a crucial role in the production of complex wear-resistant components and in expanding repair capabilities, especially for intricate wear parts with low tolerances (e.g. with cooling channels). Herein, we report a novel approach providing nickel-based alloy with an excellent tribological performance in dry sliding contacts. Laser-deposited self-lubricating nickel alloys, infused with anti-wear additives of molybdenum disulfide, nickel sulfide, copper sulfide, or bismuth sulfide, were subjected to dry sliding wear tests against an alumina ball counterbody at a temperature range of up to 800 °C. The self-lubricating alloys exhibited a significant decline in friction (43 %) and wear (45 %) at room temperature, 400 °C (friction 40 %, wear rate 55 %), and 600 °C (MoS 2 -based, friction 58 %, wear rate 75 %). The MoS 2 -based alloy coating demonstrated excellent performance characteristics up to 800 °C (friction coefficient ⁓0.25, wear rate 11 × 10−6 mm3 N−1 m−1) due to the formation of a 'glazed' tribolayer. Wear mapping allowed to identification of a critical condition for self-lubricating alloys where positive transitions in wear mechanisms led to a synergistic lubrication mode involving the formation of tribologically induced new lubricious phases such as silver molybdate or nickel-bismuth intermetallic. This work provides a comparative evaluation of the micromechanisms, surface transitions, and tribochemistry of solid lubricants at a wide temperature range and a variety of applications. • Comparative study of five solid lubricants i.e. Ag, Ag + MoS 2 , Ni 3 S 2 , CuS, or Bi 2 S 3. • Superior running-in behavior of self-lubricating alloys especially at 400, 600 °C. • Decline by 40–50 % in CoF and wear rate of self-lubricating alloys at RT and 400 °C. • Exceptional decline for Ag + MoS 2 in CoF/Wear by 58 %/75 % at 600 °C, and 70 %/33 % at 800 °C. • For Bi 2 S 3, a lubricious glazed layer rich in Nickel–Bismuth intermetallic sustains at 800 °C. [ABSTRACT FROM AUTHOR]