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Effect of Ion Nitriding Process on Tool and Mold Quality

人气: Article Source: Unknown Popularity: Issuing time: 2019-03-23 20:02
The ion nitriding furnace produced by our company performs ion nitriding treatment on different commonly used tool and mold materials under different current types, gas atmospheres, nitriding temperatures, and ammonia addition processes, and performs metallographic analysis and hardness measurement on the test pieces. The test shows that the ion nitriding process with IGBT inverter pulse power supply with narrow slot tooling is more reasonable; the ammonia addition process is beneficial to reduce the surface. Layer and increase the hardness and thickness of the nitriding layer. Keywords: ion nitriding; mold hardness; metallographic analysis; glow voltage; ion nitriding or multi-component nitriding; one of the chemical heat treatment methods developed recently. This process has fast nitriding speed, good quality of the nitrided layer, small deformation, no Pollution, energy saving, and energy saving can significantly improve the hardness, wear resistance and anti-seizure force of components, increase fatigue strength, and thereby improve the quality and service life of the tooling. There are many factors affecting the quality of ion nitriding. Literature research shows that there are mainly current types, current density, glow voltage, gas atmosphere, gas pressure, nitriding temperature and holding time. The main research content of this article is to use different pulse power sources (electrical parameters), different ion components and pressures (atmospheric parameters) to perform common ion nitriding and ma with three different power sources for materials commonly used in making tools and molds. Experiment of nitriding process, and measure its metallographic structure, surface hardness and nitrided layer thickness. Test specimens and test conditions In order to study the quality of the nitriding process with narrow slot tooling, the test specimens shown in Figure 1 were specially made, and 45 steel and 35CrMoA steels were used to make each group of test specimens. The ion nitriding process test was performed on equipment produced by Hangzhou Plasma Equipment Engineering Co., Ltd. For the ordinary ion nitriding process, the power supply is tested separately with DC power supply, BTO chopper pulse power supply and IGBT inverter pulse power supply; the current density is, the gas composition is, where N / H = 4, and the holding time is 8h. The processing temperature is 5200C, the pressure rise rate is controlled below 8Pa / h, the gas pressure is 500Pa, 650Pa, 800Pa, and the glow voltage is 500V, 650V, 800V. For the argon-nitriding process, a DC power supply is used. The gas composition is: holding time is 5h, processing temperature is 500 °, air pressure is 200Pa, current density is, and glow voltage is 750V. After the test results and analysis of the nitriding treatment, the test piece was cut open, and the metallographic analysis, hardness test, and thickness measurement of the nitriding layer were performed. Figure 2 shows the metallographic structure of 45 steel material under ion nitriding with IGBT inverter pulse power source, and Figure 2a is the top of the tank. (See Figure 1), Figure 2b is the metallographic structure at the upper part of the groove b, and Figure 2c is the lower part of the groove. Metallographic organization. Figures 3 ~ 5 show the comparison of hardness at different points a, b, and c for different materials after nitriding with DC power supply, BTO chopper pulse and IGBT inverter pulse power supply respectively; Figure 6 shows DC power supply, different Comparison of the hardness gradients of the nitrided layers of the two materials under the new treatment process. 1. As can be seen from the metallurgical micrograph in Figure 2, the compound layer at the top point a is thicker, about 15 μm; and the compound layer at the lower point c of the groove is thinner, about half of the point a (7 -8μm); the compound at the upper b is very thin, only about 2-3μm. 2. It can be seen from Figures 3 and 4 that the higher the atmospheric pressure is, the higher the nitriding hardness; among the three power sources, the nitriding hardness when using the IBGT inverter pulse power source **, followed by the BTO chopper pulse power source The hardness of the nitriding layer when nitriding with a DC power supply **. In addition, the higher the glow voltage, the higher the hardness of the nitriding layer, but the degree of influence on the three power sources is different. Among them, the impact when using IBGT inverter pulse power is greater, and the glow voltage when using IBGT inverter pulse power is nitriding. The effect is better at 700-800V and atmospheric pressure is 650-800Pa. 3. It can be seen from Fig. 4 and Fig. 5 that when nitriding is performed with an IBGT inverter pulse power supply, the top. The hardness at the place is high, and it is less affected by the glow voltage and the atmospheric pressure; but at the upper part b, it is obviously affected by the glow voltage and the atmospheric pressure; and the influence at the lower point c is also larger, but slightly smaller than the bottom . 4. It can be seen from Figure 6 that the hydrogenation process is beneficial to improve the surface hardness of the nitrided layer due to the diffusion strengthening effect of the alloy nitrides. From the distribution of the hardness gradient, it can be seen that argon nitriding is beneficial to the diffusion of nitrogen, so that There is a ν 'phase or an α + ν' phase in a certain thickness in the interior; and the direct current power supply nitriding layer for common processes is thin and has low hardness. Conclusion 1. For the ion nitriding process with a narrow slot tool, no matter which mold material is used, the effect of using an IGBT inverter pulse power supply **. 2. When using ordinary DC power supply and ordinary pulse power supply for nitriding treatment, the nitriding effect in the depth of the narrow slit is very poor, and its hardness is almost the same as that of the untreated raw materials, which is not suitable for nitriding treatment. 3. When the tooling with narrow slits is used for ion nitriding, the atmospheric pressure should be high (at 800Pa **) and the glow voltage should be high (at 780V **), but the atmospheric pressure and glow voltage cannot be increased without limit. , So it is better to switch to the current type. 4. The process of adding argon is beneficial to the diffusion of nitrogen, reducing the surface ε phase layer and enhancing the dispersion effect of nitride.

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