Strong-bonding self-lubricating nickel-matrix coatings at a wide temperature range

Abstract

The weak bond strength that affects self-lubricating coatings across a wide temperature range severely limits their application on the surfaces of high-temperature mechanical parts. To solve this problem, the strong-bonding self-lubricating NiCrAlY-Ag-BaF₂/CaF₂ coatings were produced by detonation spraying. The as-sprayed coatings exhibit high bond strengths of 65 – 75 MPa by controlling the formation of semi-molten state particles and in-situ oxides. The composite coating with 10 wt% fluoride eutectic and 20 wt% Ag shows the favorable tribological properties at a wide temperature range from room temperature to 900 °C. The combined effects, including the formation of the lubricating Ag film, the synergistic lubricating effect of BaF₂/CaF₂ and CaCrO₄ formed by tribo-chemistry at high temperature, tribo-glaze of oxides, and tribo-transfer film, contribute to favorable lubrication at a wide temperature range.