Integrated analysis of drilling tool wear

Abstract

The integrated analysis of wear of drilling tools is performed. The wear pattern is analyzed versus the build of the acting faces of drilling tools. It is found that a cooling lubricant containing a surface active substance (SAS) has influence on the axial load of the tool and on the drilling capacity. The correlation between wear and current roughness of acting faces of tools is revealed. The additive technology developed and validated for feeding cooling lubricants enables higher competitive capability of allmetal tool owing special grooves made in the drill body by 3D printing to ensure SAS inlet to the rock–drilling tool contact. The comparative study of wear of tools under vibro-percussive loading with regard to the loading condition is carried out. We studied three tools made of steel grades 65S2VA, 5KHNM and of hard alloy VK-8. An attempt is made to utilize hidden capacities of spring steel in manufacture of tool capable to operate under superposition of vibrations. For such rocks as sandstone, limestone, shale, iron ore, clay, etc., having strength categories from IV to X on the Protodyakonov scale, it is possible to use tools made of spring or structural steel, which enables considerable reduction in the cost of drilling. Structural steels used to manufacture drilling tools for hard rock drilling under superposition of vibrations sometimes can efficiently replace expensive tools made of hard alloys. Another beneficial factor is high brittle fracture resistance of instrument steels as against hard-alloy tools. The study reveals the dependence of tool durability on the tool geometry. Preliminary observations show that geometry is an essential factor for tools made of structural and instrumental steels. It is suggested that wear of instrumental steel tool insignificantly differs from hard-alloy wear. In some cases, well-hardened instrumental steel successively competes with hard alloy.