Effect of electroless bath chemistry on microstructure and tribological properties of Niₓ–B–W–hBN self-lubricating coatings

Abstract

Electroless deposition is a versatile method for fabricating Niₓ–B-based alloy and composite coatings known for superior mechanical and tribological performance across diverse industrial sectors. Using the Nix–B (x = 1, 2, 3…) notation to represent the compositional complexity of these systems, this study compares electroless Nix–B–W alloy and Nix–B–W–hBN composite coatings deposited on low-carbon steel substrates, evaluating hardness, fracture toughness, and coefficient of friction. Particular emphasis is placed on the role of hexagonal boron nitride (hBN) reinforcements as solid lubricants within the Nix‑B‑W matrix (for Nix‑B‑W‑hBN composite coating) and on identifying the key process parameters that enable the hBN‑reinforced composite to outperform the Nix‑B‑W alloy coating. The results show that incorporating hBN particles substantially increases coating hardness and fracture toughness while simultaneously lowering the steady‑state coefficient of friction under the tested load. This study highlights the interplay among bath chemistry, coating microstructure, and tribological response, providing mechanistic insight into the factors that yields the development of a mechanically and tribologically superior coating through hBN incorporation. The rational design of self‑lubricating Nix‑B‑W‑hBN composite coatings demonstrated here holds considerable potential for industrial applications requiring low friction and enhanced wear resistance. Copyright © 2026. Published by Elsevier Ltd.