On operational adaptability of wear-resistant coatings for key components in electric vehicle differentials: A case study

Abstract

During starting, rapid acceleration, and energy regeneration (with alternating forward and reverse rotation), EV differentials endure much higher instantaneous torque than conventional vehicles, greatly increasing wear and failure risk. Surface coating technologies thus offer a key strategy to enhance differential durability. However, conventional evaluation methods deviate from real service conditions, making it difficult to assess coating adaptability. This study targets the planetary gear shaft—the most wear-prone component—and develops a shaft-ring tribological test bench. Finite element simulations determined benchmark loads, replicating actual contact and motion. Wear tests on electroless nickel and DLC coatings were conducted under varying loads and lubrication. Results show electroless nickel, with lower hardness, exhibited wear under all conditions but retained partial coverage even under severe loads, maintaining surface protection. In contrast, DLC, with much higher hardness, showed negligible wear in most cases but failed catastrophically under high load and poor lubrication, where local damage propagated rapidly, exposing the substrate and causing severe adhesive wear. Thus, electroless nickel is preferable under high load/impact to prevent catastrophic failure, while DLC is favored under stable conditions for its superior hardness. These findings provide a scientific basis for coating selection and design in EV differential components.