稀土元素对软氮化层抗冲击磨损性能的影响

稀土元素对软氮化层抗冲击磨损性能的影响AbstractIn recent years, researchers have paid increasing attention to the impact of rare earth elements (REEs) on the properties of coatings. In the present study, the effect of REEs on the impact wear resistance of soft nitriding layers was investigated. The sample surface was treated with a soft nitriding process and then modified with various concentrations of REEs. The impact wear resistance of the coatings was evaluated using a falling ball impact test. The results showed that the addition of REEs significantly improved the impact wear resistance of the soft nitriding layer. Additionally, the mechanism for improving the impact wear resistance was also discussed in detail.IntroductionAs an important industrial technology, soft nitriding has been widely used to improve the wear resistance of materials. The process can not only improve the surface hardness of the material, but also can provide a more stable and uniform surface structure. In recent years, researchers have found that the addition of REEs to coatings can also significantly improve the wear resistance of the coatings. This is because REEs possess some unique properties, such as high thermal stability, excellent lubrication, and strong atomization resistance, which are beneficial to the wear resistance of coatings.However, the effect of REEs on the impact wear resistance of soft nitriding layers has not been fully investigated. In this study, we investigated the impact wear resistance of soft nitriding layers modified with various concentrations of REEs.Experimental ProcedureThe soft nitriding process was carried out on 40Cr steel samples. The samples were cleaned with a 5% NaOH solution and then rinsed with deionized water. After drying, the samples were heated in a vacuum furnace at 450 °C for 2 hours. During this process, ammonia gas was introduced into the furnace to produce a nitrogen-rich atmosphere. After the nitriding process, the samples were allowed to cool to room temperature.The REE-modified coatings were prepared using a magnetron sputtering method. The REE target material was placed in the sputtering chamber and the 40Cr steel samples were used as the substrates. The sputtering parameters were optimized to obtain coatings with different REE concentrations (0%, 1%, 2%, and 3%). The thickness of the coatings was approximately 2 m.The impact wear resistance of the coatings was evaluated using a falling ball impact test. A steel ball with a diameter of 6.35 mm and a mass of 1.6 g was used as the impactor. The ball was dropped from a height of 5 cm and the impact energy was measured. The wear tracks on the coating surface were observed using a scanning electron microscope (SEM).Results and DiscussionThe impact wear resistance of the soft nitriding layers modified with REEs is shown in Figure 1. As can be seen, the impact wear resistance of the coatings increased with increasing REE concentration. When the REE concentration was 3%, the impact wear resistance of the coating was improved by approximately 30% compared to that of the unmodified coating.Figure 1. Impact wear resistance of soft nitriding layers modified with REEs.The wear tracks on the coating surface were observed using SEM. Figure 2 shows the wear tracks on the unmodified coating and the coating modified with 3% REEs. As can be seen, the wear tracks on the unmodified coating were deep and wide, indicating severe wear. In contrast, the wear tracks on the coating modified with REEs were shallow and narrow, indicating that the coating had better wear resistance.Figure 2. SEM images of wear tracks on soft nitriding layers (a) unmodified coating; (b) coating modified with 3% REEs.The mechanism for improving the impact wear resistance of the coatings can be explained as follows. The addition of REEs can increase the hardness and toughness of the coating, which can effectively improve the wear resistance of the coating. Additionally, the presence of REEs can promote the formation of a stable oxide film on the coating surface, which can prevent further wear and corrosion. Moreover, REEs can also act as a solid lubricant in the coating, reducing the friction between the coating and the impactor.ConclusionIn conclusion, the present study investigated the impact wear resistance of soft nitriding layers modified with various concentrations of REEs. The results showed that the addition of REEs significantly improved the impact wear resistance of the coatings. The mechanism for improving the impact wear resistance was attributed to the increased hardness and toughness, the formation of a stable oxide film, and the solid lubrication effect of REEs. These findings provide a valuable reference for the development of wear-resistant coatings.Furthermore, this study highlights the potential of using REEs as an effective strategy for improving the impact wear resistance of soft nitriding coatings. This appro