Comportamento tribológico do disco de corte de microtuneladora: uma análise multiescala

Abstract

The increasing demand for infrastructure projects has driven the use of Trenchless Methods (NDM), which enable the execution of underground interventions with minimal surface impact. Among these methods, microtunneling stands out, where excavation is carried out by Microtunnel Boring Machines (mTBMs) equipped with disc cutters. These tools, manufactured from H13 tool steel, undergo continuous wear throughout the rock excavation process, requiring frequent replacements. The costs associated with the acquisition and replacement of these discs represent a significant portion of project budgets, justifying the study of their wear behavior. Historically, wear prediction tests for drilling tools have been developed without a structured connection to tribology, traditionally analyzed from the perspective of rock abrasiveness. Although various methods have been created to measure this property, the lack of a tribological approach compromises their representativeness, resulting in tests that provide only qualitative data or are disconnected from real excavation conditions. This work proposes a systemic and multiscale approach to investigate the wear and failure mechanisms of Microtunnel Boring Machine (mTBM) disc cutters. Initially, field-worn discs were analyzed in detail using macro and microscopic techniques, microhardness, and X-ray diffractometry, aiming to characterize their failure modes and material removal mechanisms. Complementarily, a new laboratory wear test was developed, employing a universal tribometer configured to simulate the contact and movement between disc cutters and rocks. The objective is to precisely quantify friction and the wear rate, overcoming the limitations of conventional tests. The results are presented in three scientific papers: the first details the characterization of failure modes; the second focuses on the validation of the laboratory method for measuring wear; and the third presents the newly proposed tribological test.