| Summary: | 碩士 === 建國科技大學 === 機械工程系暨製造科技研究所 === 101 === Tool steel of DIN 1.2367 series is one of the critical and extensive high-alloyed steels in industries. It mainly applies to gears and the molds of high-temperature environment, frequently, to the extruding mold of heat fins and the forging mold for alloy. The materials of molds don’t just need to conquer the wearing problems but also need to concern about the fraction problems that made by working-cycle stress acting on molds. However, the last researches of DIN 1.2367 tool steel mostly focused on the wearing resistance improvement and there were few investigations on the more series material fatigue fracture. This research plan of two-year period primarily investigates the dual effects of the plasma nitriding layer and vacuum heat treatment for the improvement to the low-cycle fatigue strength of DIN 1.2367 tool steel.
The first, we are going to study the characteristics of the DIN 1.2367 tool steel after adding high-quantity Mo, improving mechanical properties by vacuum heat treatment, and changing surface properties by the plasma effect of plasma nitriding. Through the plasma quality of controlling nitriding parameters (the fraction of mixing gas, the nitriding time, and the nitriding temperature), we carry on the different nitriding. And we analyze the influences of the nitriding parameters on the nitriding layer by the investigating nitriding layer technique. Among them, it includes the relations of nitriding phase, nitriding depth, diffusing depth, and slight hardness.
The second research will precede low-cycle fatigue experiments and analysis of fracture organization according to the different nitriding steels of the first year. We will discuss the influences of the plasma -nitriding and vacuum heat treatment on the fatigue life, tension strength and Youth’s module.
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