Abstract
This paper presents an auxiliary heating method to maintain a uniform specimen temperature and precisely control nitriding temperature during plasma nitriding. The surface properties and wear properties of AISI H11 steel treated by auxiliary heating plasma nitriding are investigated. Firstly, the specimens with different diffusion layers and different hardness levels are fabricated through changing the plasma nitriding temperature. Secondly, the surface properties of the plasma-nitrided H11 steel specimens are characterized by a scanning electron microscope (SEM), X-ray diffractometer, metallographic microscope and microhardness tester. The results show that the surface hardness of the plasma-nitrided specimen is almost twice as high as that of the untreated specimen. The thickness of diffusion layer increases with the increase of nitriding temperature. However, the surface hardness firstly increases and then decreases with the increase of the nitriding temperature. Finally, the wear properties of untreated and plasma-nitrided H11 steel specimens are investigated under different friction conditions. The results show that the plasma-nitriding method can significantly improve the wear resistance of AISI H11 steel. The friction coefficient fluctuations of the plasma-nitrided specimens are all lower than those of the untreated specimens. In addition, the wear rates of the plasma-nitrided specimens rise along with load, and reduce along with the sliding speed and friction temperature.
Highlights
Hot working die steel plays a vital role in the die industry due to its superior manufacturing and processing performance, and is especially suitable for metal’s thermo-plastic forming process, such as hot forging die, die casting die, hot heading die, and so on [1]
There is no study about the effects of friction test parameters on the wear properties of specimens treated by auxiliary heating plasma nitriding
This paper proposes an auxiliary heating method to maintain a uniform specimen temperature and precisely control the nitriding temperature during plasma nitriding
Summary
Hot working die steel plays a vital role in the die industry due to its superior manufacturing and processing performance, and is especially suitable for metal’s thermo-plastic forming process, such as hot forging die, die casting die, hot heading die, and so on [1]. Thermal fatigue failure and wear failure are the common failure modes of hot working die steel [2,3]. Hardness and wear resistance are two of the key performance indicators of hot working die steel. With the increase of the use requirements of hot working die steel, improving its hardness and wear resistance is always a research hotspot. Nitriding treatment is an alternative surface strengthening treatment method for AISI H11 steel, which can significantly improve its wear resistance, corrosion resistance and fatigue resistance [4]. Plasma nitriding has many advantages, such as good wear resistance, high diffusion speed, ease to control, little deformation and environment-friendliness [8,9], and is an important surface strengthening method in mold and friction parts. Understanding the wear properties of specimens treated by plasma nitriding under different friction conditions is vital to the mechanical structure design and actual use of the friction parts
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