The significance of the comprehensive score data of friction and wear at the edge, 1 / 2R and center was tested by variance analysis. The calculation results are summarized in table 4-10. The results of qt-3 and qt-3 are not consistent with those of qt-3.

Through the range analysis of orthogonal test, the best level under the most significant factor was selected firstly, combined with the results of analysis of variance, so the optimal scheme of the test taking the comprehensive score of friction and wear of different parts of lzqt600-3 ductile iron profile as the index is: t1t2s3, that is, the carburizing temperature is 580 ℃, the time is 4 h, the gas ratio is 4:1.

Friction coefficient curve and surface wear morphology of lzqt600-3 ductile iron profile after as cast and nitrocarburizing treatment were investigated. From figure (a), it can be seen that the variation law of friction coefficient of four samples is similar. At the beginning of the friction and wear test, the friction coefficient was at a high value and fluctuated greatly, then began to decrease gradually, and began to stabilize at 900 s, and then the curve showed a small range fluctuation trend.

This is because the sample just starts to slide, the surface of the sample begins to contact with the grinding disc, and the tangential force is large, so the initial friction coefficient is high. This stage is called the running in stage between friction pairs, which provides the basis for the normal friction and wear test. With the extension of the counter grinding time, the surface of the sample is ground flat under the action of friction, which leads to the contact area between the sample and the grinding disc becomes larger, so the friction coefficient of the sample gradually reaches a relatively stable value in the friction and wear experiment.