【作者】 祝贺；

【导师】 邓建新；

【作者基本信息】 湘潭大学 ， 机械工程， 2011， 硕士

【摘要】 当陶瓷切削难加工材料时,尤其是干切削,由于陶瓷刀具自身导热性差,热量容易在刀具刃口附近积聚,这种热能积聚为元素扩散提供了扩散激活能,使得陶瓷刀具与难加工材料或者切屑之间发生元素扩散成为可能,陶瓷刀具也会因为扩散磨损而降低其切削性能。本文通过试验与理论相结合的方法,研究了陶瓷刀具材料与难加工材料301不锈钢之间的元素扩散情况,分析了其元素扩散规律和元素扩散流失对刀具性能的影响,为提高陶瓷刀具使用寿命和设计新型陶瓷刀具提供理论依据。通过对菲克扩散定律的分析,得到了适合陶瓷刀具与301不锈钢之间的元素扩散浓度表达式。根据元素扩散的浓度表达式,进一步通过计算,模拟了陶瓷刀具材料与301不锈钢扩散副中Ti元素和Fe元素的扩散规律,从而为合理解释和分析扩散试验的结果提供了理论依据。同时,对元素扩散的微观机理进行了探讨。选用Al₂O₃/TiC和Si₃N₄/TiC两种以TiC为增韧方式的陶瓷刀具材料与301不锈钢进行元素扩散试验。通过试验,全面分析了在相同扩散条件下两种陶瓷刀具材料中的Ti元素与301不锈钢中Fe元素的扩散,研究了温度和持续受热时间对元素扩散程度的影响。扩散结果分析得出:在相同温度和时间扩散条件下,Al₂O₃/TiC陶瓷刀具材料与301不锈钢之间的元素扩散程度比Si₃N₄/TiC陶瓷刀具材料要更严重。扩散温度相比扩散时间对扩散的影响更大,温度越高,陶瓷刀具材料与301不锈钢之间的元素扩散越剧烈;扩散温度越高,达到同样元素扩散程度所需的时间越短。为了减少刀具的扩散磨损,根据试验可以采取以下两个方面的措施:一是利用冷却系统,降低刀具切削温度;二是在不能降低温度前提下,避免长时间切削,即在元素加速扩散的起始时间前完成加工。对元素扩散后的陶瓷刀具材料与301不锈钢组成的扩散副结合面两侧进行了显微硬度测试,测试结果反映出:靠近扩散副界面处发生扩散的材料硬度相对于远离扩散副界面未发生元素扩散的材料硬度,有了明显变化。陶瓷刀具材料在靠近扩散界面处的硬度明显比未扩散前的硬度低,随着距离扩散结合面越来越远,陶瓷刀具材料的硬度逐渐恢复到正常水平。而301不锈钢由于元素扩散,在靠近扩散界面处的硬度有明显上升,在逐渐远离扩散界面一段距离后,301不锈钢的硬度也逐渐降低到正常硬度值。虽然元素扩散深度有限,但是元素扩散的流失对陶瓷刀具材料硬度的影响深度要远大于元素扩散深度。更多还原

【Abstract】 When ceramic tools cut hard materials, especially in dry cutting, the thermal is easy to accumulate near the edge of ceramic tools owing to its low thermal conductivity. The thermal energy can provide activation energy for elements diffusion, which is possible to make elements diffusion between ceramic tools and the difficult processed materials couple. Because of this, ceramic tool will reduce cutting performance. Through theory analysis and experiment research, this paper studied the elements diffusion process between ceramic tools and difficult-to-machine material, 301 stainless steel, systemically investigated the laws of diffusion and the influence of cutting tools performance on element diffusion. The aim of this paper is to prolong the life of ceramic tools and to provide theory for designing new ceramic tools.Expression of element diffusion concentration that adapt to ceramic tools and 301 stainless steel was calculated through Fick’s second laws of diffusion analysis. Through further calculate, we simulated the diffusion rules on the element Ti which is in ceramic tools and the element Fe which is in 301 stainless steel. It provided foundation of theory for analyzing diffusion experiments. Microscopic mechanism in element diffusion between ceramic tools and 301 stainless steel has been observed and discussed.Two ceramic tools of Al₂O₃/TiC and Si₃N₄/TiC, both of which had been toughened by TiC were chosen for element diffusion experiment with 301 stainless steel. Through experiments, the diffusion of Ti and Fe was comprehensively analyzed, and the connection of temperature and time with diffusion effect between ceramic tools material and 301 stainless steel was reviewed systemically. The analysis showed that the diffusion degree of Al₂O₃/TiC with 301 was serious than Si₃N₄/TiC with 301 under the same high temperature and keeping-temperature time; diffusion temperature has more effect on diffusion than time. To same diffusion degree, the higher diffusion temperature is, the shorter time needs. According to the result of experiments, we should take same actions for decrease the diffusion wear of cutting tools: the first is to reduce the cutting temperature; the second is better to finish cutting process before the initiative time of accelerating diffusion.Tool hardness was tested after diffusion experiment. It is showed that tool hardness of materials had diffused obviously changed. Hardness near the diffusion interface greatly decreased, and hardness far away from the interface got to a normal level gradually. But the hardness of workpiece near diffusion interface was obviously higher than its normal hardness, and gradually decreased to normal hardness far away diffusion interface. Although it is only dozen microns took place between ceramic tool materials and 301 stainless steel, the effect caused by diffusion was more than the distance of elements diffusion.更多还原