Corrosion behavior of WC-Co tool bits in simulated (concrete, soil, and mine) solutions with and without chloride additions

Abstract

The WC-Co materials are widely used in the different industry for a variety of applications and are being exposed by the different corrosive environments, and subsequently, binder (Co) phase leach out and hence WC grains pulled out from the matrix and caused early stage of failure. This study mainly focused on the finding of the comparative corrosion behavior of WC-Co materials using all the simulated environments (sea, concrete, soil, and mine) which simulates the more actual corrosive environment conditions for the WC-Co hardmetals that usually being faced by the tool bits during the industrial application. The present work examined the electrochemical behavior of WC-Co hard metals in a solution of deionized water, 3.5% and 5% NaCl as well as with and without chloride contaminated simulated soil, concrete, and mine solutions using cyclic polarization tests, linear polarization, and electrochemical impedance tests. The corrosion morphology of corroded WC-Co has also been observed after the cyclic polarization tests to understand the corrosion mechanisms in the aforementioned solutions. EDX analyses have confirmed the dissolution of binder (Co) phase. Optical profilometer has been used to obtain the extent of corrosion attack using average roughness values, and the Raman spectroscopy has confirmed the presence of hydrated WO3 corrosion product formed on the surface after cyclic polarization tests. Different duration of immersion tests has been used to understand the dissolution behavior of Co and the formation of a stable corrosion product layer. Electrochemical results have confirmed that the corrosion rates of WC-Co materials have strongly influenced by the electrolyte composition, pH, and salinity of the solutions.