Preparation and Properties of High-Temperature Self-Lubricating Materials Based on H13 Steel
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Preparation and Properties of High-Temperature Self-Lubricating Materials Based on H13 Steel Cheng Jiang, Huajun Wang, Menglu Li, Songshan Yan, Zhenhua Yao, and Qingyang Liu Submitted: 17 May 2020 / Revised: 21 September 2020 / Accepted: 22 October 2020 High-temperature self-lubricating materials based on H13 steel are prepared by the powder metallurgy method. The sintering process, phase addition and high-temperature testing of the material are studied so that the mechanical and wear performance of the composites can be optimized. The results show that the optimum sintering process is 2 h at a temperature of 1250 °C. When the contents of Cr2C3 and CaF2 are 10%, the mechanical and sintering properties of the composites are acceptable. The relative density reaches 80.2% and the bending strength reaches 720.2 MPa. Moreover, CaF2 effectively reduces the friction coefficient and wear rate of the material. The friction coefficient decreases to a minimum of 0.24, but the wear rate increases to a maximum of 7.26 3 1025 mm2/min at a load of 1065 g. Cr2C3 helps to alleviate the oxidation of the composites, and the precipitation of CaF2 causes network cracks to reduce the thermal fatigue performance. Keywords
H13 steel, high-temperature wear, microstructure, powder metallurgy, self-lubrication composite
1. Introduction At present, the extensive use of graphite-based lubricants effectively improves the wear, thermal fatigue, stress corrosion and oxidation defects that are likely to occur during actual die production processes (Ref 1-3). Yang et al. (Ref 4) proposed that water-based graphite as a lubricant with fine graphite particles evenly suspended in water. During hot forging, the mold is lubricated and sprayed onto the heated mold surface by a dilute water-based lubricant. However, the maximum operating temperature of liquid grease does not exceed 300 C (Ref 5). The working temperature of hot forging dies is often kept above 600 C. Liquid oils are prone to volatilization and a rapid decline in viscosity. Their lubrication and friction-reducing effects are reduced, and the surface of the mold is directly in contact with the blank, leading to an increase in the friction coefficient of the mold material and severe wear. It is worth noting that volatile lubricating grease is harmful to human health and causes pollution to the ecological environment. Compared with liquid lubricating grease, solid lubricants have a strong load carrying capacity, high-temperature chemical stability, high utilization rate and strong adhesion (Ref 6-9). A discontinuous lubricating film with low shear strength is formed on the surface, but it is not enough to cover the entire composite material surface when the self-lubricating material is subjected to frictional stress and environmental temperature. Cheng Jiang, Huajun Wang, Menglu Li, Zhenhua Yao, and Qingyang Liu, School of Materials Science and Engineering, Wuhan University of Technology, Wuhan 430070 Hubei, China; and Songshan Yan, School of Mechanical Engin
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