This study explores the impact of substrate hardness on the tribological properties of graphene oxide (GO) solid lubricant coatings on NiP alloy layers coated Q235 steel. Through adjustment of electroless plating parameters, NiP alloy layers with varying hardness levels were produced to investigate their effects on the wear resistance and friction performance of GO coatings. The methodology included substrate preparation, electroless NiP alloy plating, electrophoresis deposition of GO, and detailed analysis of the structural, mechanical, and tribological characteristics of the coatings. These findings underscore the crucial role of substrate hardness in the tribological efficiency of GO coatings. A specific hardness level emerged as optimal, significantly enhancing the distribution and effectiveness of the GO tribofilm. This uniform and continuous tribofilm led to notable improvements in the wear resistance and a reduction in friction coefficients. Moreover, this optimal hardness ensured continuous lubrication and superior load-bearing capabilities, substantially prolonging the lifespan of the coatings. Substrates with hardness levels that were either too high or too low were observed to hinder the maintenance of a consistent tribofilm, thereby negatively impacting the tribological performance of the coating. This research highlights the importance of achieving an optimal substrate hardness to enhance the tribological performance of solid lubricant coatings. By optimizing the balance between the substrate hardness and integrity of the tribofilm, this study paves the way for developing more efficient, durable, and environmentally sustainable mechanical components, offering new insights into tribological science and materials engineering.