# Changes in the Tribological and Mechanical Properties of Nimonic 90 Superalloy After Irradiation with Swift Xenon Ions

## TL;DR

Irradiating Nimonic 90 with xenon ions changes its wear resistance and hardness, with some recovery at high doses.

## Contribution

First observation of radiation annealing in Nimonic 90 after xenon ion irradiation.

## Key findings

- High fluence xenon irradiation causes radiation annealing and hardness recovery in Nimonic 90.
- Low fluence irradiation degrades mechanical and tribological properties due to radiation-induced defects.
- Long-range effects of irradiation impact wear resistance beyond the projected ion range.

## Abstract

What are the main findings?

Swift Xe ion irradiation alters wear resistance of Nimonic 90.

Long-range effect observed beyond projected ion range.

High fluence (5 × 1014) induces radiation annealing and hardness recovery.

What is the implication of the main finding?

Nimonic 90 is limited in tribological applications under irradiation.

Radiation damage can both degrade and partially heal surface layers.

Nimonic 90 remains valuable in aerospace and reactor components, but not in friction nodes.

The article presents the results of research on the effect of 160 MeV xenon ions irradiation on the mechanical and tribological properties of the Nimonic 90 superalloy. The alloy samples were irradiated with xenon ion fluences ranging from 1 × 1014 to 5 × 1014 Xe24+/cm2 at a temperature of 60 °C. The investigations revealed significant changes in the crystal structure of the material, including the formation of new phases and partial amorphisation of the surface layer, particularly pronounced at the highest irradiation fluence. Measurements of microhardness, coefficient of friction, and wear revealed a deterioration in the mechanical and tribological properties of the samples irradiated with fluences of 1.0 and 2.5 × 1014 Xe24+ ions/cm2, attributed to the formation of radiation-induced defects. Increased friction and wear were observed at depths greater than the predicted range of xenon ions, indicating the occurrence of a long-range effect. After irradiation with a 5.0 × 1014 Xe24+ ions/cm2 fluence, a radiation annealing effect was observed, leading to a partial reduction in the earlier damage and resulting in improved microhardness and reduced wear. To our knowledge, this is the first observation of a radiation annealing effect under these specific irradiation and test conditions. The findings suggest limitations in the application of the Nimonic 90 superalloy in environments exposed to intense ionizing radiation, such as nuclear reactors.