Highlights •The self-oxide-cleaning effect of B makes the CuNiInB coating prepared by atmospheric plasma spraying have a low oxygen content of ~ 0.4%. •The limited oxide inclusion in coating leads to deposition of highly dense coating with a porosity of ~0.3 %. •The adhesion wear resistance of the CuNiIn coating is improved due to the enhancement of coating microhardness. •The fretting wear resistance of the CuNiInB coating is five times higher than that the conventional APS CuNiIn coatings. Abstract Atmospheric plasma-sprayed (APS) CuNiIn coatings have been widely used for fretting wear protection in many important areas such as aircraft engines for decades. However, its fretting wear performance is much lower than the bulk counterpart due to the poor inter-splats bonding quality within the APS coating. The oxide-film on the deposited splats formed by the reaction of the in-flight metallic droplet with the surrounding oxygen is believed to the dominating factor that hinders the metallurgical bonding formation between adjacent splats. In the present work, it was attempted to deposit dense CuNiIn coatings with enhanced inter-splat bonding by deposition of oxide-free CuNiIn droplets. To achieve oxide-free droplets at atmospheric condition, CuNiIn powders pre-alloyed with 2 wt% and 4 wt% of B, which could act as a deoxidizer, were used as the feedstock powders. Individual in-flight droplets were collected with liquid N2 to clarify the so-called “self-oxide-cleaning” effect. Results show that the CuNiInB particles without oxide scale resulting from oxide-free droplets were achieved with B-alloyed powders while an oxide scale covered on CuNiIn particle surface. The B pre-alloyed coatings with a dense microstructure reveal a much lower oxide content of ~0.4 % in comparison with 1.6 % for conventional CuNiIn coating. Fretting wear tests show that the B-strengthened dense CuNiIn coating obviously presents an enhanced ability to inhibit fatigue crack propagation and suppress delamination-dominated wear. The fretting wear resistance of the CuNiInB coating is increased by a factor of five compared with the conventional APS CuNiIn coatings.