Korean Journal of Metals and Materials (대한금속재료학회지)

The Korean Institute of Metals and Materials (대한금속재료학회)
권호 표지

Microstructure, Hardness, and Fracture Toughness of Surface Composites Fabricated by High-Energy Electron-Beam Irradiation of Fe-Based Metamorphic Alloy Powders and VC Powders

철계 반비정질 합금 분말과 VC 분말을 고에너지 전자빔으로 투사하여 제조된 표면복합재료의 미세조직, 경도, 파괴인성

  • Nam, Duk-Hyun (Center for Advanced Aerospace Materials Pohang University of Science and Technology) ;
  • Do, Junghyun (Center for Advanced Aerospace Materials Pohang University of Science and Technology) ;
  • Lee, Sunghak (Center for Advanced Aerospace Materials Pohang University of Science and Technology)
  • 남덕현 (포항공과대학교 항공재료연구센터) ;
  • 도정현 (포항공과대학교 항공재료연구센터) ;
  • 이성학 (포항공과대학교 항공재료연구센터)
  • Received : 2008.07.15
  • Published : 2008.10.25
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Abstract

In this study, surface composites were fabricated with Fe-based amorphous alloy powders and VC powders by high-energy electron beam irradiation, and the correlation of their microstructure with hardness and fracture toughness was investigated. Mixture of Fe-based metamorphic powders and VC powders were deposited on a plain carbon steel substrate, and then electron beam was irradiated on these powders without flux to fabricate surface composites. The composite layers of 1.3~1.8 mm in thickness were homogeneously formed without defects and contained a large amount (up to 47 vol.%) of hard $Cr_2B$ and $V_8C_7$ crystalline particles precipitated in the solidification cell region and austenite matrix, respectively. The hardness of the surface composites was directly influenced by hard $Cr_2B$ and $V_8C_7$ particles, and thus was about 2 to 4 times greater than that of the steel substrate. Observation of the microfracture process and measurement of fracture toughness of the surface composites indicated that the fracture toughness increased with increasing additional volume fraction of $V_8C_7$ particles because $V_8C_7$ particles effectively played a role in blocking the crack propagation along the solidification cell region heavily populated with $Cr_2B$ particles. Particularly in the surface composite fabricated with Fe-based metamorphic powders and 30 % of VC powders, the hardness and fracture toughness were twice higher than those of the surface composite fabricated without mixing of VC powders.

Keywords

Acknowledgement

Supported by : 한국과학재단

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