Effect of Solution Treatment on Wear Resistance of a New Type of Austenitic High Manganese Low Temperature Steel

In response to the wear issue of a new type of austenitic high manganese low-temperature steel in LNG storage tanks, this paper investigated the effects of different solution treatment temperatures on microstructure, mechanical properties, and wear resistance, as well as the correlation between the three. 25 Mn high manganese steel was solid-solution treated at 950, 1 000, 1 050 and 1 100 ℃ for 0.5 hours, and the microstructure, wear profile, and wear scar morphology of the sample were characterized using optical microscopy, white light interferometer, scanning electron microscopy, and energy dispersive spectroscopy. The results showed that with the increase of solution treatment temperature, the alloy compound gradually dissolved into the crystal, leading to the diameter of the crystal gradually becoming larger. When the solution temperature was 1 100 ℃, the crystal diameter was the largest, 87.9 μm. Due to the dissolution of carbides and the increase of grain size, the surface hardness of high manganese steel gradually decreased with the increase of solution temperature. After solution treatment at 1 100 ℃, the hardness of the steel decreased to the lowest, about 261 HV. In addition, the tensile strength of steel first increased and then decreased with the increase of solution temperature, with the optimal tensile strength, yield strength, and strain hardening rate exhibited at 1 000 ℃. It was speculated that the reason may be related to the dissolution of grain carbides and the increase of crystal diameter. Carbides would generate stress concentration during the stretching process, leading to a decrease in tensile performance. As the carbides dissolved, the stress concentration effect decreased, so the tensile performance gradually enhanced. At the same time, the alloy compounds in the metal were also dissolving, leading to the increase of the crystal diameter and the weakening of the fine grain strengthening ability of the steel, so the tensile properties began to decline again. In the friction performance test results, it could be seen that the average friction coefficient on the surface of high manganese steel first increased, then decreased, and then increased with the solution treatment temperature. At 1 000 ℃, it decreased to the lowest point due to oxidation friction, about 0.39, and the wear rate was 0.49 ‰, demonstrating the optimal wear resistance. EDS analysis was conducted on the worn surface and debris at 1 000 ℃, and the results showed that oxygen elements were uniformly distributed on the worn surface. The main components of the debris were Si, Al, and O elements. This indicated that during the friction process, the steel undergone an oxidation reaction, forming an oxide layer film, resulting in a decrease in the friction coefficient. At the same time, it could be seen from the microscope that the wear scar surface of high manganese steel after heat treatment at 1000 ℃ was densely covered with uniform carbides, which leaded to the hardness increase of nearly 50.6% after wear. Similar conclusions could be obtained from the work hardening ability. Therefore, after solution treatment at 1 000 ℃, the steel's hardness increased rapidly due to its excellent work hardening ability, so the wear amount was the lowest. Due to the increase in solid solution temperature, the crystal diameter increased, reducing the plasticity of the friction surface, leading to a transformation of the wear mechanism. The friction and wear mechanism shifted from the combination of particle wear and fatigue wear to adhesive wear, with particle wear as the auxiliary.