Influence of the hottest plasma nitriding process

The influence of ion nitriding process on the quality of tools and dies

[Abstract] for the commonly used tool and die materials, ion nitriding treatment is carried out under different current types, gas atmosphere, nitriding temperature and ammonia adding process, and metallographic analysis and hardness measurement are carried out on the test pieces. The test shows that the plasma nitriding process with IGBT inverter pulse power supply is more reasonable for narrow slit tools and dies; Ammoniation process is beneficial to reduce the surface. Layer and increase the hardness and thickness of nitriding layer

key words: plasma nitriding tool and die hardness metallographic analysis glow voltage

plasma nitriding or multicomponent co nitriding is one of the chemical heat treatment methods developed recently. This process has the characteristics of fast nitriding speed, comfortable use, good quality of nitriding layer, small deformation, no pollution, energy saving, solar terms and so on. It can significantly improve the hardness, wear resistance, bite resistance and fatigue strength of parts, So as to improve the quality and service life of tools and dies

there are many factors affecting the quality of ion nitriding. Literature research shows that the main factors are current type, current density, glow voltage, gas atmosphere, gas pressure, nitriding temperature and holding time. The main research content of this paper is to use different pulse power sources (electrical parameters), under different gas compositions and pressures (atmosphere parameters), to carry out the experiments of common ion nitriding and Ma nitriding process of three different power sources for the materials commonly used in making tools and dies, and to measure their metallographic structure, surface hardness and nitriding layer thickness

test pieces and test conditions

in order to study the nitriding process quality of narrow slit tools and dies, the test pieces are specially shown in Figure 1, and one group of test pieces are made of 45 steel and 35CrMoA steel respectively

for the ordinary ion nitriding process, the power supply is tested with DC power supply, BTO chopper pulse power supply and IGBT inverter pulse power supply respectively; The current density is, the gas composition is nh3+n2, where n/h=4, the holding time is 8h, the treatment temperature is 5200c, the pressure rise rate is controlled below 8pa/h, the gas pressure is 500pa, 650pa and 800pa respectively, and the glow voltage is 500V, 650V and 800V respectively

for the argon nitriding process, DC power supply is used, the gas composition is nh3/ar=1:2, the holding time is 5h, the treatment temperature is 500 °, the air pressure is 200Pa, the current density is, and the glow voltage is 750V

test results and analysis

after nitriding treatment, cut the specimen for metallographic analysis, hardness test and nitriding layer thickness measurement. Figure 2 shows the metallographic structure of 45 steel material under ion nitriding with IGBT inverter pulse power supply, and figure 2A shows the top of the tank. (see Figure 1), figure 2B shows the metallographic structure of the upper part of the groove, and figure 2C shows the lower part of the groove. Metallographic structure of. Figure 3 ~ Figure 5 show the hardness comparison of different materials at points a, B and C after nitriding with DC power supply, BTO chopper pulse and IGBT inverter pulse power supply respectively; Figure 6 shows the comparison of hardness gradient of nitriding layer of two materials under DC power supply and different treatment processes

1. It can be seen from the metallographic structure photo in Figure 2 that the compound layer at point a on the top is thick, about 15 μ m； The thickness of the compound layer at point C at the lower part of the groove is thinner, about half of that at point a（ μ m)； The compound at the upper part B is very thin, about only μ m。

2. It can be seen from Figure 3 and Figure 4 that the higher the atmosphere pressure, the higher the nitriding hardness; Among the three power supplies, the nitriding hardness is the highest when using IBGT inverter pulse power supply, followed by BTO chopper pulse power supply, and the maintenance cost is the lowest when using direct current power supply for nitriding. In addition, the higher the glow voltage is, the higher the hardness of the nitriding layer is, but the degree of influence on the three power supplies is different. Among them, the influence is greater when using IBGT inverter pulse power supply. When using IBGT inverter pulse power supply for nitriding, the glow voltage is better when 70 Chinese enterprises have the talent to produce independently and find their own plastic extrusion machine V and the atmosphere pressure is PA

3. It can be seen from Figure 4 and figure 5 that when nitriding with IBGT inverter pulse power supply, the top. Its hardness is high, and it is less affected by glow voltage and atmosphere pressure; But in the upper part B, it is obviously affected by glow voltage and atmosphere pressure; The influence at point C in the lower part is also larger, but slightly smaller than that at the bottom

4. It can be seen from Figure 6 that the hydrogenation process is conducive to improving the surface hardness of the nitrided layer, which is caused by the dispersion strengthening effect of alloy nitrides; It can be seen from the distribution of hardness gradient that argon nitriding is conducive to the diffusion of nitrogen, so that there is ν' Phase or α+ν' Phase exists; The nitriding layer of DC power supply used in ordinary process is thin and the hardness is low

conclusion

1 For the plasma nitriding process of narrow slit tools and dies, no matter which kind of die material is used, the effect of IGBT inverter pulse power supply is the best

2. A detailed analysis of the accuracy of spring torsion testing machine with ordinary DC StarTech power supply and ordinary pulse power supply when nitriding, the nitriding effect at the depth of the narrow gap is very poor, and its hardness is almost the same as that of untreated raw materials, so it is not suitable for nitriding

3. When plasma nitriding is carried out on tools and dies with narrow slots, the atmosphere pressure should be high (800pa is the best), and the glow voltage should be high (780v is the best), but the atmosphere pressure and glow voltage cannot be increased indefinitely, so it is a better method to use current type

4. Argon adding process is conducive to nitrogen diffusion and reduce surface ε The dispersion effect of phase layer and strengthened nitride

references

1 Yang Xingkuan et al IGBT inverter pulse power supply for plasma nitriding and plasma heat treatment Metal heat treatment, 1999, 11:

2 Xia Guohua et al Modern heat treatment technology Beijing: Ministry of Ordnance Industry Press, 1997

3 Qian miaogan et al Modern surface technology Beijing: China Machine Press, 1999

4 Zhou Xiaozhong et al Plasma heat treatment technology Beijing: China Machine Press, 1992

5 Gucaixiang et al Ammonia ion nitriding process Metal heat treatment, 2000, 2:

6 Chen Fangsheng et al Study on rare earth catalytic ion nitriding process Metal heat treatment, 1999:

scientific research fund support project of Zhejiang Provincial Education Commission (end)