Enhanced Mechanical Properties of Sintered Iron via Cyclic Induction Heat Treatment
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HEMICAL THERMODYNAMICS AND THERMOCHEMISTRY
Enhanced Mechanical Properties of Sintered Iron via Cyclic Induction Heat Treatment Yifei Chena, Runjian Jianga, Chengsong Zhanga, Dazhi Chena, and Guodong Cuia,* a
School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu, 610031 China *e-mail: [email protected] Received December 28, 2019; revised December 28, 2019; accepted March 11, 2020
Abstract—In order to improve the mechanical properties of sintered iron, the cyclic induction heat treatment (CIHT) was applied to produce ultrafine microstructure on surface. The surface microstructure of refined grains and micropores, and the related mechanical properties were investigated. Results indicated that the refined grain (24.60–3.66 μm) and micropore (9.52–1.67 μm) contribute to a substantial improvement in compressive yield strength (177–555 MPa) and surface microhardness (123.0–300.8 HV0.1) of the sintered iron samples. Grain refinement was ascribed to the high nucleation rate and short grain growth time, which is due to rapid processing and a large number of microporous interfaces. Meanwhile, the micropore structure was refined due to grain refinement in resintering process. Thus, the CIHT is considered as a feasible method to improve mechanical properties of iron-based sintered alloys, providing them with more promising applications on key structural parts. Keywords: surface strengthening, cyclic induction heat treatment, sintered iron, ultrafine microstructure DOI: 10.1134/S0036024420130075
1. INTRODUCTION As an important way to improve the surface properties of sintered iron, surface strengthening can enhance the microhardness, yield strength and fatigue life of the parts [1–3]. Lamim et al. [4] had researched the duplex surface treatment of sintered iron by plasma nitriding and plasma carburizing at low temperature, and the results shown that the surface microhardness has been enhanced significantly. Cui et al. [5] fabricated sintered iron by spark plasma sintering (SPS). The strength of sintered iron was enhanced by quenching after carburization. It obtained a higher yield strength level (256 MPa), which has increased by 90% comparing non-treated sintered iron. Bendo et al. [6] studied the nitriding of surface Mo-enriched sintered iron. Their results show that surface nitriding of Moenriched sintered iron leads to the formation of a composite layer with different morphology depending on the nitriding temperature. The microhardness was also improved significantly. Although the research above all has reported some progress in improving the performance of sintered iron, they still don’t get enough mechanical properties to solve the problem of applying sintered iron to key components. Compared to other surface strengthening technologies, IHC has many advantages including low cost, energy saving, high production efficiency and no pollution [7, 8]. IHC can refine grains and micropores at the same time, which optimizes the microstructure of sintered
iron [9–11]. What is more, CIHT is a more eff
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