Correlation of microstructure with hardness and wear resistance of VC/steel surface-alloyed materials fabricated by high-energy electron-beam irradiation

2009

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Iron-based surface composites were fabricated with Fe-based metamorphic alloy powders and VC powders by high-energy electron beam irradiation, and the correlation of their microstructure with hardness and fracture toughness was investigated. Mixtures of metamorphic powders and VC powders were deposited on a plain carbon steel substrate, and then the electron beam was irradiated on these powders without flux, to fabricate surface composites. The composite layers 1.3 to 1.8 mm in thickness contained a large amount (up to 47 vol pct) of hard Cr 2 B and V 8 C 7 particles formed in eutectic colony regions and inside colonies, respectively. The hardness of the surface composites was approximately 2 to 4 times greater than that of the substrate because of Cr 2 B and V 8 C 7 particles. According to the microfracture observation of the composite fabricated with mixing 30 wt pct VC powders, microcracks initiated at coarse V 8 C 7 particles ins inside colonies as well as at Cr 2 B particles in colony regions, and were connected with other microcracks in a zigzag shape. Thus, it showed a higher fracture toughness and hardness twice as high as the composite fabricated without mixing VC powders.

Section: Discussionmentioning

confidence: 99%

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

2009

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“…The matrix located inside solidification cells consists primarily of martensite because it cools rapidly by heat transfer after the temperature exceeds 3000 °C during the beam irradiation. [29,30] In the (CrB,MoB)/steel surface composite layers, borides are densely precipitated along cells, and the matrix inside cells is composed of martensite.…”

Section: Discussionmentioning

confidence: 99%

Correlation of microstructure with hardness and wear resistance in (CrB, MoB)/steel surface composites fabricated by high-energy electron beam irradiation

2006

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Correlation of microstructure with hardness and wear resistance of (CrB,MoB)/carbon steel surface composites fabricated by high-energy electron beam irradiation was investigated in this study. Three kinds of powder mixtures, i.e., 50CrB-50MgF 2 (flux), 50MoB-50MgF 2 , and 25CrB-25MoB-50MgF 2 (wt pct), were placed on a plain carbon steel substrate, which was then irradiated with the electron beam. In the specimens fabricated with flux powders, the surface composite layer of 0.8 to 1.3 mm in thickness was successfully formed without defects, and contained a large amount (up to 48 vol pct) of Cr 1.65 Fe 0.35 B 0.9 or Mo 2 FeB 2 in the martensitic matrix. The hardness and wear resistance of the surface composite layer were directly influenced by the hard borides, and thus were about 3 to 7 times greater than those of the steel substrate. Particularly, in the surface composite fabricated with CrB and MoB powders, the hardness of eutectic solidification cells and martensitic matrix was very high, and borides formed a network structure along cells, thereby leading to the best hardness and wear resistance. These findings suggested that the high-energy electron beam irradiation was useful for the development of surface composites with improved hardness and wear resistance.

“…[7,8] In particular, the irradiation of high-energy accelerated electron beam toward the substrate in the air has been newly developed to fabricate surface composites. [9,10,11] When high-energy electron beam is irradiated on a metal substrate surface where powders are evenly deposited, the substrate surface and powders are melted and solidified to form a surface composite layer, thereby fabricating surface composites.…”

Section: Introductionmentioning

confidence: 99%

Correlation of microstructure with hardness and wear resistance of surface composites fabricated by high-energy electron beam irradiation of Fe-based metamorphic powders

et al. 2006

Self Cite

In this study, surface composites were fabricated with Fe-based metamorphic powders by high-energy electron beam irradiation, and the correlation of their microstructure with hardness and wear resistance was investigated. Fe-based metamorphic powders were deposited on a plain carbon steel substrate, and then electron beam was irradiated on these powders without flux to fabricate a one-layered surface composite. A two-layered surface composite was also fabricated by irradiating electron beam again onto the powders deposited on the one-layered surface composite. The composite layers of 1.3;1.9 mm in thickness were homogeneously formed without defects and contained a large amount (up to 48 vol pct) of hard and fine Cr 2 B crystalline phases in the Cr 0.19 Fe 0.7 Ni 0.11 matrix. Since the hardness and wear resistance of the surface composite layers were directly influenced by hard Cr 2 B phases, they were two to three times greater than those of the steel substrate. In particular, the twolayered surface composite showed a high hardness of ;300 VHN even at 750°C, as well as at room temperature, because Cr 2 B phases and the Cr 0.19 Fe 0.7 Ni 0.11 matrix were hard and thermally stable.