| Summary: | 碩士 === 國立臺灣大學 === 機械工程學研究所 === 95 === The purpose of this study is to understand the characteristics of solid nitriding. The effect of solid nitriding on the wear resistance of cold working tool steel such as SKD11, SKH51 and DC53 will be discussed in this article. The above steel sample was nitrided at various temperatures for different time. Then, the microstructure, hardness distribution, nitrogen contents and wear resistance of the nitrided layer was examined for each solid nitriding condition. Moreover, above experimental data was compared with those of conventional NH3 gas nitriding. The results were summarized as follows:
1.In order to obtain an effective surface hardness and the
more dense compound layer, the temperature ranging from
500℃ to 550℃ was the optimal temperature for the solid
nitriding.
2.The compound layer of steel after the solid nitriding
was rather dense and not easy to crack or spall off. It
is not necessary to remove the layer by grinding before
application.
3.The steel has hardening effect as long as the solid
nitriding temperature over 480℃. The wear resistance of
nitrided layer increases with increasing nitriding
temperature or time. The dies and machine parts should
be nitrided under appropriate conditions depending on
their application reguirement. Besides, the wear
resistance of the nitrided layer was the best for the
steel nitrided at 550℃. As to the steel nitrided at
600℃, the holes will appear in the compound layer and
nitrides will become coarse. Therefore, both the surface
hardness and the wear resistance will decrease.
4.The nitriding at low temperature 480℃~500℃ was not
easy to produce deformation, so this method could be
applied to the precision machine parts.
5.The compound layer of solid nitriding was permeated with
not only nitrogen but also carbon. Although the nitrided
layer was not as thick as that of the gas nitriding,
the compound layer had better toughness and wear
resistance.This point was similar to Tufftriding.
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