Effect of process parameters on the microstructure and mechanical properties of vacuum hot-press sintered Co-50 mass% Cr alloys

ABSTRACT

In the present research, two different compositions of submicron-structured cobalt (800 ± 45 nm) and chromium (700 ± 50 nm) powders are mixed to fabricate Co-50 mass% Cr alloys by the vacuum hot-press sintering technique. This study imposes various hot-press sintering temperatures (1150, 1200, 1250 and 1300°C) and pressures (20, 30, 40 and 50 MPa) while maintaining the sintering time at 1 h, respectively. The experimental results show that the optimum parameters of hot-press sintered Co-50 mass% Cr alloys are 1200°C at 50 MPa for 1 h. Meanwhile, the sintered density reaches 7.73 g cm⁻³, the closed porosity decreases to 0.31%, and the hardness and transverse rupture strength values increase to 80.6 ± 0.3 HRA and 1052.9 ± 17.5 MPa, respectively. Grain growth is not obviously generated after 1200°C hot-press sintering at 50 MPa for 1 h. Consequently, the optimal solid-phase sintering process effectively improved hot-press sintered Co-50 mass% Cr alloys, which resulted in the good properties.

KEYWORDS:

• Co-50 mass% Cr alloys
• hot-press sintering
• closed porosity
• hardness and TRS

Acknowledgements

This research is supported by the ASSAB STEELS TAIWAN CO., LTD. The authors would like to express their appreciation for Dr Harvard Chen, Michael Liao and Mr Meng-Yu Liu.

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes on contributors

Shih-Hsien Chang: 1993–1995, MS. in Materials Science and Engineering, National Cheng Kung University; 2001–2006, Ph.D. in Materials Science and Engineering, National Cheng Kung University; 2015.2-present, Professor, Department of Materials and Mineral Resources Engineering, National Taipei University of Technology.

Chih-Yao Chang: 2015–2017, MS. in Institute of Materials Science and Engineering, National Taipei University of Technology.

Kuo-Tsung Huang: 2001–2007, Ph.D. in Materials Science and Engineering, National Cheng Kung University; Lecturer, Department of Auto-Mechanics, National Kangshan Agricultural Industrial Senior High School, Kaohsiung.

Ming-Wei Wu: 2004–2007, Ph.D. in Materials Science and Engineering, National Taiwan University; 2017.2-present, Professor, Department of Materials and Mineral Resources Engineering, National Taipei University of Technology.