engleski

ANALYSIS OF THE CRACK FORMATION IN ASIS M2 HIGH- SPEED TOOL STEEL DURING UTILIZATION

Tool steels are carbon, alloyed or high-speed steels, produced and processed under the tool steel manufacturing practices to meet special requirements. The advancements in tool steel engineering properties enabled work efficiency improvements in industrial applications. The high-speed tool steels (HSS) are complex iron- based alloys containing carbon, chromium, vanadium, molybdenum, tungsten or substitutional amount of cobalt. The chemical composition of HSS is designed to achieve the highest attainable hardening response, high wear resistance, high resistance to softening effect at elevated temperatures, and good toughness necessary for effective use in industrial cutting operations. The ASIS M2 is a molybdenum- based medium alloyed HSS with good machinability. Favorably designed chemical composition and adequately performed heat treatment assure good combination of toughness, wear resistance and hardness enabling its utilization as twist drills, taps, milling cutters, saws, and knives. It is also commonly used as cold work punches. The research was performed on two samples of ASIS M2 punchers to estimate the cause of the shorter service life. In sample 1 the crack nucleation occurred after 50.000 punched marks, while in sample 2 cracking initiated after 20.000 punched marks. To indicate the cause of sample 2 shorter service life, the results of chemical composition analysis, metallographic analysis, and microhardness measurements were compared. The higher amount of carbide forming elements in sample 2 led to the solidification of higher number of eutectic carbides and precipitation of secondary carbides in intercellular regions. The microstructure analysis indicated significantly higher number of carbide particles in sample 2. The presence of carbide particles led to the texture development and impacted crack propagation direction. Higher amount of carbide particles in sample 2 caused higher crack dissipation and material layering with a decrease in crack propagation depth and shorter service life.

ASIS M2, high-speed tool steels, cracking, service life, microstructure, carbides

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