Influence of Austempering Heat Treatment on Microstructure and Mechanical Properties of Medium Carbon High Silicon Steel

International Conference on Materials, Alloys and Experimental Mechanics 2017

材料科学;金属学;机械制造

Palaksha, P.A.^1 ; Ravishankar, K.S.^1

Department of Metallurgical and Materials Engineering, National Institute of Technology, Surathkal Karnataka, India^1

关键词: Austempering temperature;    Characterization studies;    Hardening response;    High-silicon steel;    Lower temperatures;    Microstructure and mechanical properties;    Retained austenite;    X ray diffractometers;   

Others  :  https://iopscience.iop.org/article/10.1088/1757-899X/225/1/012006/pdf
DOI  :  10.1088/1757-899X/225/1/012006

学科分类：材料科学（综合）

来源: IOP

【 摘 要 】

In the present investigation, the influence of austempering heat treatment on the microstructure and mechanical properties of medium carbon high silicon steel was evaluated. The test specimens were machined from the as-received steel and were first austenitised at 900 °C for 45 minutes, followed by austempering heat treatment in salt bath at various temperatures 300 °C, 350 °C and 400 °C for a fixed duration of two hours, after that those specimens were air-cooled to room temperature. The characterization studies were carried out using optical microscope, scanning electron microscope (SEM) and x-ray diffractometer (XRD) and then correlated to the hardness and tensile properties. Results indicate that, the specimens austempered at lower temperature i.e. at 300 °C, which offered high hardness, tensile strength and lower ductility (1857 MPa and 13.3 %) due to the presence of acicular bainite i.e. lower bainite and also some martensite in the microstructure. At 350 °C, reduction in the tensile strength and hardness was observed, but comparatively higher ductility, which was favored by the presence of bainite laths i.e. upper bainitic structure along with higher retained austenite content. Finally at 400 °C, reduction in both ductility and tensile strength was observed, which is due to the precipitation of carbides between the banite laths, however good strain hardening response was observed at austempering temperatures of 350 °C and 400 °C.