The friction and wear properties of lzqt600-3 ductile iron profile at different positions were tested. Among them, the comprehensive score is to comprehensively consider the influence of friction coefficient and wear rate on the material, and the two evaluation indexes of friction coefficient and wear rate are comprehensively scored with the ratio of 0.5:0.5. Because the wear rate is very low, in order to make a better comprehensive score, the wear rate is increased by 4 orders of magnitude before the comprehensive score.

The comprehensive score data of friction and wear performance of edge, 1 / 2R and center were analyzed by range analysis, and R value was calculated, and the results as shown in Fig. 1 were obtained. The results show that the order of the factors affecting the comprehensive score of friction and wear in the center of the orthogonal experiment is as follows: the permeating temperature T > the gas proportion s > the nitriding time t; the factors influencing the comprehensive score of friction and wear at the edge and 1 / 2R are in the order of gas ratio s > infiltration time t > infiltration temperature T. The surface hardness and effective depth of hardened layer have important influence on the wear resistance of the samples. In the actual working conditions, the higher the surface hardness, the greater the effective hardening depth, and the longer the service life of the material. Therefore, the primary and secondary order of influencing factors on the core of lzqt600-3 ductile iron profile is selected as the standard. The primary and secondary order of the influence of nitriding parameters on the comprehensive score of friction and wear of lzqt600-3 ductile iron profile is as follows: nitriding temperature T > gas proportion s > nitriding time t.

The evaluation index of the data is intuitive analysis of the influence of each factor on the comprehensive score of friction and wear of the sample, which can show the influence degree of each factor more clearly. The results are shown in Fig. 2. The smaller the friction coefficient and wear rate of the material, the better its wear resistance is. Therefore, the lowest comprehensive score level under each factor should be selected. It can be seen from Fig. 2 that the increase of NH3 content has a great influence on the comprehensive score of friction and wear of the samples, while the influence of two factors, namely, the time and temperature, is not obvious.