Effect of chromium nitride coatings and cryogenic treatments on wear and fretting fatigue resistance of aluminum

• Lifetime of overhead conductors can be improved using CrN coated suspension clamps.
• Deep cryogenic treatments improved the fretting fatigue resistance of aluminum.
• Stick-slip regimes generate material transfer from the conductor to the clamps.
• CrN reduced clamp damage and material transfer from the conductor to the clamps.
• Aluminum oxide wear debris are mainly generated when full relative slip occurs.

As commonly known, the endurance of overhead conductors is limited by fretting fatigue. The most severe fretting fatigue damage occurrence is the suspension clamp, as a superposition of many different loads occurs in the conductor/clamp assembly. Therefore, this paper focuses on two modification methods, which aim to reduce the fretting fatigue loading in such assemblies. The investigated modification methods are a deep cryogenic treatment and a surface coating. To study the effect of both methods on the duration of overhead conductors, comparative fretting fatigue tests with real conductor/clamp contacts were carried out. A reduced amount of wire breaks was found for both modification methods. Especially the first wire break occurred significantly delayed using deep cryogenic treated and coated suspension clamps (20% for the deep cryogenic treated and 60% for the tests with coated clamps). The post mortem analysis showed severe damage marks in the suspension clamps. The use of the surface coating led to a reduced amount of damage in the suspension clamps.