Characterising and reducing seizure wear of inconel and incoloy superalloys in a sliding contact

Superalloys, such as Inconels and Incoloys, are extensively used where high strength is a requirement. However, where these materials are required to slide against one another, particularly with poor or no lubrication, high friction levels and seizure are commonly seen to occur, which can cause component failure. In this work seizure characteristics of three superalloys (Inconel 718 and Incoloys 945 and 945X) were investigated, uncoated, coated with Armoloy (a hard, thin, dense chrome coating with a micro-nodular surface texture) and plasma nitrided in dry sliding conditions. A rig purpose built for initiating seizure was used. It involves sliding a ball against a disc at constant speed while the load is increased. Tests are designed to last less than one rotation so that the wear scar can be analysed, along with friction data, to establish at which load seizure occurred. Balls made from Inconel 718 were used along with sliding velocities ranging between 0.1 and 0.25 m/s with a load range of 0-1400 N. Tests were repeated twice. Repeatable behaviour was achieved in the tests and from the results obtained, zones/points corresponding to “seizing”, “seizure” and “seized” were identified based on previous definition from the literature. Friction coefficients behaviour was also characterised. It was found that Inconel 718 and Incoloy 945 performed better than Incoloy 945X. Applying an Armoloy coating increased the seizure load and led to lower friction rates. The application of plasma nitriding led to a more consistent (although high) friction coefficient, but less surface damage occurring.