Auger Electron Spectroscopy Analysis of W diffused from WC Grain into Co Regions in Cutting Tools

Abstract

  In tungsten carbide tools fabricated by sintering WC and Co, mechanical properties are strongly governed by the distribution and number of W atoms that diffuse from WC grains into Co regions. This paper reports on the use of Auger electron spectroscopy (AES) to determine the concentration of W atoms diffused into a Co region across the WC/Co interface in a tungsten carbide tool. Directly analyzing the distribution of diffused W in the Co region near the WC/Co interface by AES is difficult because the Auger signal derived from the WC grain by the backscattering effect cannot be ignored. We propose a practical method for estimating the W concentration across the WC/Co interface by taking into account the backscattering effect. We prepared a WC/Co model sample with negligible W diffused into the Co region. The AES line profiles of W and Co across the WC/Co interface in the model sample agreed with the line profiles calculated by Monte Carlo (MC) code taking into account the backscattering effect. Then, we measured AES line profiles over a WC/Co/WC region in a real tungsten carbide tool with W diffused into the Co region and we calculated profiles without W diffusion into the Co region by MC code. The W distribution in the Co region was estimated by taking into account the backscattering effect: The calculated profile was subtracted from the measured profile to remove the background component introduced by the backscattering effect.