热成形工具的离子渗氮和气体渗氮

A Aomparison of Plasma and Gaseous Nitriding for Tools in Hot Massive Forming

用于热成形的工具承受的载荷比较复杂。为了使这类工具能经受高载荷,应对其进行渗氮处理,也可进行液体氮碳共渗,很少进行离子渗氮。然而,与气体渗氮相比,离子渗氮有一定的优越性,例如,较易实施局部渗氮、比较清洁等。高合金钢零件表面往往有起保护作用的氧化层,但也易于进行离子渗氮,因为在渗氮前可通过溅射将氧化层去除掉。介绍了用于渗氮处理的钢为常用来制作热成形工具的1.2367钢和1.2344钢。渗氮试验在气体渗氮炉和两台不同的离子渗氮炉中进行,因此可以对气体渗氮与离子渗氮和在不同炉子中进行的离子渗氮进行对比。其中的一台离子渗氮炉中还安装了活性屏,从而除了普通的离子渗氮外,还可以进行活性屏离子渗氮(ASPN)。从是否适宜处理锻造工具的角度探讨了不同渗氮工艺的优缺点。

Tools for hot massive forming are exposed to complex loads. In order to resist the high loads, the surfaces of the tools are nitrided. As an alternative to gaseous nitriding the tools are also treated by salt bath nitrocarburising. Plasma nitriding is only rarely used. But the plasma treatment has some advantages over gaseous nitriding. For example partial treatments can be carried out more easily and cleaner. Steels with higher alloy content can be easily nitrided because the protecting oxide layer on the surface, which sometimes occurs, can be removed by a sputtering step before nitriding. The investigations concern the nitriding treatment of the steels 1. 2367 and 1. 2344, which are often used in hot massive forming. The nitriding experiments could be carried out in a gas nitriding furnace and two different plasma nitriding furnaces, therefore a comparison of the nitriding media gas and plasma was possible as well as a comparison of the treatment in different plasma nitriding furnaces. One of the furnaces was also provided with an active screen, therefore it was possible to do active screen plasma nitriding （ASPN） in addition to conventional plasma nitriding. The advantages and disadvantages of the different treatment technologies were discussed in respect of their suitability for forging tools.