Fatigue life extension by electroless nickel infiltration plating

Introducing artificial closure material into a fatigue crack has been shown to be able to retard the crack and give considerable life extension. Most of the previous work employed polymers as closure material which will disintegrate under a high service temperature. Moreover, infiltrations of these closure materials were made with the cyclic loading interrupted and the cracks held open at some static load. This will give an intense initial retardation. However, retardation will die down quickly if it is not severe enough to arrest the crack right away. To improve on the above drawbacks, the current work employed electroless nickel-plating as closure material. A more efficient infiltration method has been developed to allow on-line infiltration plating without interrupting the cyclic loading. To shed more light on the possible applicability of this technique to practical service loading, the retardation behaviour under different static infiltration loads, different load ratios, variations in loading history and loading frequencies have been investigated. It has been found that by combining static and dynamic infiltration plating, a fatigue crack can be brought to arrest quickly even under a loading frequency of 10 Hz.