Effect of quenching and tempering on microstructure and mechanical properties of 410 and 410 Ni martensitic stainless st
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Amir Momeni and Niloofar Aieni Materials Science and Engineering Department, Hamedan University of Technology, Hamedan 6516913733, Iran
Hamid Keshmiri Esfarayen Steel Complex, Esfarayen 1589673711, Iran (Received 5 August 2016; accepted 28 November 2016)
In this research, the effect of austenitizing at 900–1100 °C and tempering at 250–650 °C on the microstructure and mechanical properties of 410 and 410 Ni martensitic stainless steels was investigated. The transformation of austenite to ferrite surrounded the austenitizing within the temperature range of 900–1050 °C. The grain size and hardness measurements proved that austenitizing at 1050 °C leads to the partial dissolution of carbides without a considerable growth of austenite grains. The mechanical tests showed two peaks in strength and troughs in ductility by tempering at 450 and 650 °C due to the formation of primary and secondary carbides. The better ductility and fracture toughness in 410 Ni, comparing to 410, were attributed to the effect of Ni on stacking fault energy. Fractured surfaces revealed ductile fracture of the samples tempered at low temperatures, e.g., 250 °C. However, after tempering at 450 and 650 °C, 410 showed a brittle fracture and 410 Ni exhibited a dual intergranular-brittle fracture mechanism.
I. INTRODUCTION
Heat treatment is a crucial step in the processing route of different types of steels. The precise control of heat treatment can improve the mechanical properties and microstructure. Generally speaking, heat treatable steels are those which have tendency for the martensitic transformation through quenching of austenite. The martensitic stainless steels (MSSs) are a major group of high-alloy heat treatable steels which provide high strengths and good corrosion resistance for some industrial applications such as steam turbine blades, valves, shafts, screws, and plastic molds.1,2 Their successful performance necessitates a good combination of strength and ductility which is acquired by a precise control of heat treatment. The heat treatment for MSSs includes austenitization, quenching, and tempering. While austenitization-quenching leads to a hard martensitic structure with low ductility, tempering restores ductility at the expense of hardness and provides a desired combination of hardness and ductility. Therefore, a sort of parameters in austenitization-quenching and tempering steps affects the mechanical properties.3,4 The formation of a single-phase austenitic structure and the dissolution of carbides and other phases are the major aims of austenitizing. For this purpose, the Contributing Editor: Jürgen Eckert a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2016.485
austenitizing temperature should be high enough to dissolve all carbides into austenite.5 On the other hand, chromium carbides which are often present in MSSs control the grain growth and participate in the formation of finer austenite structure before quenching.6 The finer austenite grain size which is obtained at lo
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