Failure behavior of cemented tungsten carbide materials: a case study of mining drill bits

Abstract

The present work is mainly focused on the macroscopic and microscopic examination of failed tungsten carbide (WC-Co) drill bits to find the root cause of the inserts failure. Different failed WC-Co tool bits have been observed macroscopically and found that the inserts have failed due to shear-off, cracks, and gradual wear. The FE-SEM and AFM micrographs have been used to understand the different degradation and the tribocorrosion mechanisms of WC-Co inserts. Typical shape change mechanisms of individual WC grains have also been studied in detail with the help of FE-SEM micrographs, which have been influenced by the tribocorrosion in the presence of the mining environment. Ultrasonic cleaning method has been used to clean the inserts for the microscopic examinations. Various morphologies of fragmented WC grains have been examined to understand the shape change mechanisms of WC grains. The different electrode potential between the Co binder and the WC grains is the primary cause of the micro-galvanic form of corrosion. Hence, in the present study the wear and corrosion mechanisms of WC-Co insert along with the possible approaches to reduce the tribocorrosion have been discussed in detail. It was found that the proper understanding of tribocorrosion mechanisms is essential for the selection, development, and advancement of the suitable WC-Co tool materials.