Effect of Thin TaN on Tensile Characteristics of Tantalum

Abstract

The purpose of this study is to reveal the effect of surface nitriding on the tensile characteristics and fracture morphology of tantalum. In this study, two types of gas nitride treatment, with different surface hardness, were introduced to cold rolling tantalum. A constant tensile speed was given in the specimen until fracture. In order to investigate the nominal strain and surface strain distribution, an image measurement system was used. Hardness distribution in across the thickness of the specimen and surface morphology of fractured specimens were also evaluated. Test results showed that the fracture state of the nitride specimens could be divided into 3 stages. At the first stage, in the elastic region, due to the presence of a TaN layer, the Young’s modulus of the specimen increased as compared to that of pure tantalum. At the second stage in the strain hardening region, the tiny crack of the TaN layer was propagated due to the increase in strain. Therefore, pseudo-strain hardening would be observed because of the progressive propagation of surface cracks. At the final stage, the surface crack propagated across the width, and thus, the deformation was concentrated.