The effect of high-energy electron-beam irradiation on microstructural modification of a high-speed steel roll

Self Cite

The main objective of the present study is to analyze the microstructural modification of the surface hardened by the irradiation of high-energy electron beam in 0.18 pct C and 0.38 pct C plain carbon steels. Steel samples were irradiated using an electron accelerator (1.4 MeV), and the detailed microstructures of the irradiated surface were examined. Upon irradiation, the ferrite-pearlite structure near the sample surface was changed to the dual-phase structure, i.e., ferrite and martensite, and fine particles or needlelike lamellae were observed in the ferrite/martensite interface. In order to investigate these complex microstructures as well as the martensitic transformation mechanism, the simulation test, including thermal cycles of abrupt heating and quenching, was carried out. The test results indicated that the irradiated surface was heated up to about 1100ЊC and then quenched to room temperature, which was enough to obtain the surface hardening through martensitic transformation. Thermal analysis of the irradiated surface was also carried out for systematic understanding of the microstructural modification in terms of the irradiation parameters such as beam travel speed.

Section: Discussionmentioning

confidence: 97%

Microstructural modification of plain carbon steels irradiated by high-energy electron beam

Suh

Lee²,

Koo

1997

Self Cite

“…[29,30] Since the martensite is rapidly softened by tempering at high temperatures, there will be restrictions in high-temperature applications. In this study, a fabrication idea of surface composites with Fe-based metamorphic powders was suggested to improve surface properties, and a considerable amount of amorphous phases were expected to be present in the fabricated surface composites because the high-energy electron beam irradiation method had fast heating and cooling rates.…”

Section: Discussionmentioning

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

Nam

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.

“…[31,32] Since the martensite is rapidly softened by tempering at high temperatures, there will be restrictions in high-temperature applications. In the (CrB,MoB)/steel surface, composites fabricated in the current study; however, borides are homogeneously distributed inside the martensitic matrix.…”

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

Nam

2006

Self Cite

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.