Gear shafts in ships and machines work under heavy loads. Striking a metal surface with rapid ultrasonic pulses makes it harder, smoother and longer-lasting by squeezing its outer layer. But warmth during operation may weaken this benefit. We treated a steel gear shaft this way, then kept it warm. The surface stayed hard and smooth; heat only slightly eased the squeezing, while hardening remained intact. Computer predictions matched our tests, supporting safe use of this method in warm service.

This study examines deep-sea gear lubrication challenges under extreme conditions, including high pressure, with a focus on EHL (elasto-hydrodynamic lubrication) theory and interface texturing advances. Critical gaps remain in multi-physics coupling and synergistic texture-coating interactions. The paper proposes a research roadmap integrating multi-scale modelling, surface engineering optimization, experimental validation, and industrial implementation to enable robust deep-sea transmission systems.

A thermoelastic hydrodynamic lubrication (TEHL) model with interface micro-texture (IMT) evaluates load-bearing capacity. The model characterises the textured interface with micro-convex peaks (MCPs) by introducing an equivalent scale factor and an optimised distribution density function. A mathematical framework quantifies anti-scuffing load-bearing capacity (ASLBC) under steady-state TEHL, revealing coupled stiffness–damping in a micro-textured meshing interface (MTMI) under dynamic loading.