The wear resistance of micro spade drills and D-shaped tool materials

High-speed steel (HSS) is commonly used in producing micro-cutting tools due to its excellent abrasive wear resistance, especially under high rotational speeds and low thermal activation conditions. Numerous studies have focused on enhancing the microstructural properties of HSS further to improve the wear resistance of these micro tools. However, abrasive machining processes like grinding and lapping are employed during the manufacturing of micro tools such as spade drills, milling cutters, and taps. In these processes, controlling the wear rate is crucial, as it directly impacts the achievable material removal rate. Therefore, maintaining wear rate stability is more critical than only measuring the total amount of wear. In this context, this study aims to evaluate the wear of HSS with various microstructures using a variation of the pin-abrasion test (PAT). Pins of M3 class 2 (referred to as M3/2) HSS obtained from three different manufacturers were tested using SiC abrasive articles (320# mesh) under a constant load of 0.35 MPa and variable rotary speeds between 0.5 and 6.0 m/s. The materials were evaluated, and the type and quantity of primary carbides (MC and M₆C) present in their microstructures were determined with the aid of scanning electron microscopy (SEM) and X-ray energy dispersive spectroscopy (EDS). The results demonstrated a relationship between wear behavior and carbide size and distribution: materials with larger carbides with a non-uniform distribution exhibited greater wear rate instability. This implies that micro tools made from HSS should have a microstructure characterized by a uniform distribution of small carbide particles to ensure stability during fabrication. Additionally, a method for testing wear rate stability was proposed.