Effect of ion-induced dislocation hardening on diffusion and gas swelling mechanisms in carbide ceramics

Abstract

The paper presents the assessment results of the application of the method of ion modification of the near-surface layer of SiC ceramics in order to create a dislocation hardening effect to enhance the resistance of ceramics to helium swelling and embrittlement. Interest in this topic is due to the possibilities of expanding the practical application of ion modification in the field of structural materials used in extreme conditions. The choice of heavy ions for the targeted modification of the near-surface layer of ceramics is based on a hypothesis, which is based on the assumption that the isolated structural distortions created in the near-surface layer during the interaction of incident ions with the crystal structure can have a barrier effect on the ballistic nature of the migration of complex defects of the HeeV type, as well as implanted helium into the material due to changes in the dislocation density in the damaged layer. According to tribological test data, it was established that the use of Ar8þ, Kr15þ ions with fluences of 1012 - 1013 ion/cm2 allows surface wear rate reduction during mechanical wear tests during determination of the dry friction coefficient. The observed effect of enhancement of the resistance to the damaged layer destruction caused by the accumulation of structural damage due to a rise in the concentration of implanted He2þ ions (in this case, the irradiation fluence and the value of atomic displacements are implied) is due to the creation of additional dislocation defects and distortions caused by the impact of heavy ions. The assessment results of the change in the values of the hardness of the damaged layer along the trajectory of the He2þ ions revealed that the creation of structural distortions due to preliminary irradiation with heavy ions creates additional barriers for the diffusion expansion of the damaged layer in depth, from which it follows that the created effect of dislocation hardening due to irradiation with low fluences of heavy ions in the near-surface layer plays a positive effect on enhancement of the resistance to destruction caused by gas swelling.