| Summary: | 碩士 === 國立臺灣大學 === 機械工程學研究所 === 89 === In order to understand the behavior of 410 stainless steel under gas nitriding at high temperature. We divided the experiment into three parts in the research: 1.High temperature gas nitriding: Steel samples were heated over A1 transformation temperature. We can discuss the influence of nitriding rate; hardness, distribution and microstructure of 410 stainless steel were investigated from the change of nitriding time, the nitriding temperature, ammonia flow-rate, and the nitriding pressure. 2.High temperature two-stage gas nitriding: After gas nitriding at high temperature, steel samples were treated in traditional gas nitriding at lower temperature. We expect that we can find the best hardness distribution of 410 stainless steel, and apply the result of the research to tapping screws. 3. The comparison of high temperature two stage gas nitriding to traditional gas nitriding: From the hardness distribution view, we analyze this two stage nitriding methods. The results were summarized as followed:
1.After the samples of 410 stainless steel are nitriding at high temperature, the hardness of surface layer becomes softer, because of forming α-Fe phase; the core of the samples can be harden, because of forming martensite structure.
2.After high temperature two-stage gas nitriding, the surface layer hardness distribution of 410 stainless steel is approximately satisfying the requirement of tapping screws.
3.After traditional gas nitriding, the proportion of alloy in 410 stainless steel is high, still can result in the depth of nitriding is deficiency and hardness gradient is too high even the surface layer hardness of 410 stainless steel is extremely hard.
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