Application of the Q-n-P-Treatment for Increasing the Wear Resistance of Low-Alloy Steel with 0.75% C
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APPLICATION OF THE Q-n-P-TREATMENT FOR INCREASING THE WEAR RESISTANCE OF LOW-ALLOY STEEL WITH 0.75% C V. G. Efremenko,1, 2 V. I. Zurnadzhi,1 Yu. G. Chabak,1 O. V. Tsvetkova,1 and A. V. Dzherenova1
UDC 669.1.017
We study the influence of the Q-n-P-treatment including the interrupted quenching followed by holding at 250–350°C on the microstructure, hardness, and abrasion resistance of 75KhG2C steel. It is shown that the Q-n-P-treatment leads to the formation of a structure with elevated (27.5%) content of residual austenite. The procedure treatment with quenching interrupted at 100°C followed by the holding at 250°C for 10 min increases the abrasive wear resistance of steel by 8% as compared to the fully quenched state with a much lower hardness (57 and 63 HRC, respectively). Keywords: Q-n-P-treatment, steel, austenite, martensite, wear resistance.
The technology of thermal treatment of metal products is continuously improved by the creation and development of its new direction called “Quenching and Partitioning” (Q-n-P) [1]. The indicated procedure enables one to get high-strength states of steels that do not contain any high-cost alloying elements and to create multiphase structures in steels with high contents of residual austenite capable of manifestation of the TRIP-effect [2]. The Q-n-P-technology includes the following stages [3, 4]: “Q” stands for quenching with interruption of cooling at a temperature t1 in the interval between points M s and M f and “P” means partitioning, i.e., the procedure of heating, holding at a temperature t 2 which lies above the point M s and is sufficient for the activation of the diffusion of carbon, and final cooling. In the stage “P,” carbon diffuses from martensite into austenite, thus increasing the amount of residual austenite [5]. Under loading, this austenite is transformed into strain-induced martensite, which guarantees a simultaneous increase in the strength and plasticity due to the realization of the TRIP-effect [2, 6]. As usual, the Q-n-P treatment is used for the processing of steels with low and medium contents of carbon [7, 8]. Note that the application of this technology for steels with more than 0.5% C remains poorly studied in the literature. Moreover, the influence of the Q-n-P-treatment on the wear resistance of steel is, in fact, almost not investigated (with the exception of [9]) despite the fact that this method is promising from the viewpoint of formation of metastable austenite. In [10–15], it was shown that the strain-induced martensitic transformation of austenite in the process of wear strongly increases the wear resistance of steels and cast irons. In hypereutectoid steels, the required amount and degree of metastability of austenite is fairly easily attained by the procedure of ordinary quenching due to the dissolution of secondary carbides, which affects the position of point M s . In steels with amounts of carbon close to the eutectoid content (0.7–0.8%), the elevated level of alloying is necessary to get larger amounts of residual austenite. In t
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