Papers by Author: Duk Hyun Nam

Abstract: This study aimed at investigating the ballistic performance of Zr-based bulk metallic glass/Ti surface composites fabricated by high-energy electron-beam irradiation. The ballistic impact test was conducted on surface composite plates to evaluate the ballistic performance. Since the surface composite layers were observed to block effectively a fast traveling projectile, while many cracks were formed in the composite layers, the surface composite plates were not perforated. The surface composite layer containing ductile β dendritic phases showed the better ballistic performance than the one without containing dendrites because dendritic phases could hinder the propagation of shear bands or cracks.

Abstract: The present study is concerned with the improvement of hardness and wear resistance in (Cr3C2,CrB)/carbon steel surface composites fabricated by high-energy electron beam irradiation. Two kinds of powder mixtures, 50Cr3C2-50STS304 and 50CrB-50STS304 (wt.%), were placed on a plain carbon steel substrate, which was then irradiated with electron beam. The surface composite layer of 1.0~1.3 mm in thickness was successfully formed without defects, and contained a large amount (up to 58 vol.%) of Cr7C3 or Cr1.65Fe0.35B0.9 particles in the austenite or martensite matrix. The hardness and wear resistance of the surface composites were 2~3 times higher than those of the steel substrate according to hard particles. Particularly, the surface composite fabricated with CrB powders showed excellent wear resistance because selective wear of the matrix was considerably reduced.

Abstract: This study aims at correlating microstructure with hardness and corrosion resistance of surface alloyed materials fabricated with Fe-based metamorphic powders by an accelerated electron beam irradiation method. The surface alloyed materials contained 48 vol.% of hard Cr2B crystalline phases in the Cr0.19Fe0.7Ni0.11 matrix, and thus its hardness was 2.5 times greater than that of the steel substrate. The corrosion resistance of the surface alloyed materials was better than that of an STS304 stainless steel or coatings fabricated by high-velocity oxygen fuel spraying of Fe-based metamorphic powders because the Cr0.19Fe0.7Ni0.11 matrix of the surface alloyed layers and coating was selectively corroded, while Cr2B borides were retained inside pits. These findings suggested that the fabricated surface alloyed materials presented good application possibilities as excellent wear- and corrosion-resistant materials.