A comparison of mechanical properties of borides formed on pure Nb and W

Abstract

In this study, some mechanical properties of bondes formed on pure niobium and tungsten were investigated. Boronizing heat treatment was performed in a solid medium consisting of Ekabor powders at 940°C for 2, 4 and 8 hours. The presence of WB on the surface of pure tungsten and the formation of NbB <inf>2</inf> on the surface of pure niobium were confirmed by XRD analysis. Optical and SEM studies revealed an almost uniform, and compact boride layers on the surface of the pure niobium and tungsten. Experimental results showed that longer boronizing time results in thicker boride layers. The thickness of WB layer ranged from 10 to 42 ?m, and the thickness of NbB<inf>2</inf> layer ranged from 8 to 22 ?m with some scatter. The hardness of borided specimens decreased with the distance from the surface to the interior of the test material. The hardness of the boride on the pure tungsten was 2500 DPN while the hardness of the substrate was 445 DPN. Meantime, the hardness of the boride on the pure niobium was 2500 DPN while the hardness of the substrate was 110 DPN. © Institute of Materials Engineering Australasia Ltd. © 2008 Elsevier B.V., All rights reserved.