Effects of annealing treatment on microstructure and hardness in the 28 wt% Cr cast iron with Mo/W addition

Authors

  • Kittikhun RUANGCHAI Department of Physics, Faculty of Science, Naresuan University, Phitsanulok, 65000, Thailand
  • Ruangdaj TONGSRI Powder Metallurgy Research and Development Unit (PM-RDU), Thailand National Metal and Materials Technology Center, Pathum Thani, 12120, Thailand
  • John Thomas Harry PEARCE Panyapiwat Institute of Management, Nonthaburi 11120, Thailand
  • Torranin CHAIRUANGSRI Department of Industrial Chemistry, Faculty of Science, Chiang Mai University, ChiangMai 50200, Thailand
  • Amporn WIENGMOON Department of Physics, Faculty of Science, Naresuan University, Phitsanulok, 65000, Thailand

Keywords:

High chromium cast iron, Microstructure, Annealing, Hardness, Carbide

Abstract

In this study, the effects of annealing on the hardness and microstructure of 28 wt% Cr-2.6 wt% C iron with 1.4 wt% Mo/1 wt% W addition have been investigated. The as-cast samples were heated to 800℃ and held for 4 h followed by slow cooled with a cooling rate of 20℃h-1 to 500℃. Microstructures were characterized by X-ray diffractometry, optical microscopy, scanning electron microscopy and energy-dispersive X-ray spectroscopy. Vickers macro-hardness and micro-hardness were measured. It was found that the as-cast microstructure in the hypoeutectic 28 wt% Cr iron without Mo or W addition consisted of primary austenite dendrite, eutectic M7C3 carbide and martensite. In the iron with 1.4 wt% Mo addition, multiple eutectic carbides of M7C3, M23C6 and M6C were observed. In contrast the addition of 1 wt% W changed the structure to hypereutectic containing primary M7C3, eutectic M7C3 and martensite. After the annealing heat treatment, ferrite +secondary carbides and some pearlite were present in the irons, due to decomposition of austenite during annealing. The macro-hardness in the as-cast condition of the iron without alloying and the irons with 1.4 wt% Mo/ 1 wt% W addition were 506, 529, and 576 HV30, respectively. Annealing heat treatment reduced the macro-hardness to about 390, 463, and 428 HV30, respectively.

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Published

2021-06-27

How to Cite

[1]
K. RUANGCHAI, R. TONGSRI, J. T. H. PEARCE, T. CHAIRUANGSRI, and A. WIENGMOON, “Effects of annealing treatment on microstructure and hardness in the 28 wt% Cr cast iron with Mo/W addition ”, J. Met. Mater. Miner., vol. 31, no. 2, pp. 89-95, Jun. 2021.

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Original Research Articles