Development of cowb rei̇nforced nanocomposi̇tes

It has been demonstrated that composites produced using the crystallization method of metallic glasses have high hardness values but relatively lower fracture toughness values. In similar studies found in the literature, the amount of boron (B) in the alloy was systematically increased, and then the composite material was produced by crystallizing the selected metallic glass alloy from the obtained alloy system. However, it has been observed that this increase in B content accelerates the formation of Ni solid solution and CoWB. As a result of X-ray diffraction (XRD) analyses conducted to characterize the alloys produced with low boron content, it was determined that four different alloys with 15% B content had a completely amorphous structure with a 0.3 mm section thickness. However, it was determined that none of the alloys containing 15% B with a thickness of 0.5 mm were completely amorphous. Among the alloy systems with a boron content of 15% and a section thickness of 0.3 mm, the Ni49Co18W18B15 (CD4) metallic glass alloy, which was determined to be completely amorphous, was selected for composite production. It was observed that 3 of the alloys with a thickness of 0.3 mm and containing 13% B were not amorphous, and none of the alloys with a thickness of 0.5 mm were amorphous. Since the highest amount of Ni was desired in this alloy group, the fully amorphous Ni51Co18W18B13 (CD8) metallic glass alloy was chosen for composite production. The composite production was carried out by crystallizing the metallic glass alloy at an isothermal temperature of 900 K for varying durations between 25 and 200 minutes. The microstructure, mechanical properties, and corrosion behavior of the Ni49Co18W18B15 and Ni51Co18W18B13 alloys, chosen as precursors, were examined as part of the thesis study. As a result of the conducted analyses, it was determined that the composites produced by the crystallization of the Ni49Co18W18B15 metallic glass alloy reached the highest hardness value of 1325 HV during a 125-minute heat treatment period. It has been determined that the composites produced by the crystallization of the Ni51Co18W18B13 metallic glass alloy reached the highest hardness value of 1294 HV during a 150-minute heat treatment period. The fracture toughness values obtained from the Ni49Co18W18B15 and Ni51Co18W18B13 composites subjected to a 200-minute heat treatment duration, with different loads of 19.6 N and 49 N applied, are in the range of 9-10 Mpa.m½. The corrosion resistances (Ikor) of the obtained Ni49Co18W18B15 and Ni51Co18W18B13 composites in 1M HCl, 1M H2SO4, 3.5% NaCl, and 1M NaOH solutions were measured. As a result of the measurements, it was revealed that the Ni49Co18W18B15 and Ni51Co18W18B13 composites have relatively high corrosion resistance compared to other studies in the literature due to the high amount of nickel present in the alloy.