Integrated failure analysis of tri-cone drill bits using experimental techniques

The tri-cone drill bit is crucial for drilling hard rock formations during diamond mining. Its premature failure leads to downtime and productivity loss (12 failures/month, lifespan 0- 2000 m (3500–4000 m expected)) in a local Botswana diamond mine. Consequently, it is essential to understand the failure characteristics of the bit to improve its wear resistance, durability, and performance in the challenging drilling environments. This study employed macroscopic, microscopic and chemical analyses, to investigate failure modes, mechanisms, and underlying causes of drill bit failures. Failure modes identified from macroscopic analysis were abrasive wear, plastic deformation, and cracks on the cones, pull-out, fractures, cratering, flattening and one-sided wear of the inserts. Failure mechanisms identified from microscopic analysis revealed abrasion, tribo-chemical wear and fatigue. The root causes of failures were the direct impact, inclusions in cone the material, intermix and the presence of hard materials such as quartz in the kimberlite. A critical observation in the progression of failure was that abrasive wear on the cone initiates microcracks, leading to pull-out of insert, which results in uneven stress distribution, causing fractures and imbalanced insert wear that accelerates drill bit degradation. Among the proposed mitigation measures are: manufacture of the cone body using of H13/TiC composite materials for improved hardness, toughness, and high-temperature stability; Investigating bonding materials and techniques to improve the insert-cone body adhesion and using condition monitoring techniques (e.g., temperature sensors. These findings inform material selection for longer drill bit lifespan, reduced breakdown costs, and remanufacturing for sustainable mining practices. • Tri-cone drill bit failures include abrasive wear, insert pull-out, fracture and wear • Root causes of failure include impact and sliding action, rock intermix in the bit • Abrasive wear on the cone triggers all other failure modes • Cone material selection and insert shank redesign are proposed as mitigation measures