The major objective of this thesis was to explore an intelligent manufacturing method which is capable to fabricate high entropy alloys (HEAs) efficiently, and then to design new types of HEAs for use within a nuclear reactor environment. The microstructures, phase characterization and mechanical properties of alloys were investigated.
Powder arc additive manufacturing (PAAM) having a high level of controlling local forming procedure was established to fabricate HEAs in-situ. This new manufacturing process possesses time and cost saving, and rapid cooling rate which can reduce the segregation of material in comparison to traditional methods. AlCoCrFeNi2.1 eutectic HEA which simultaneously possesses high strength and high ductility was used as a prime example to verify the feasibility of PAAM system. Different times (1,3,6) remelting process which is typically applied in arc melting to improve the homogeneity of prepared material was compared in this research. The applied layer-remeltin
In this study, the composites of the micro drill with nano WC powder, Co powder, TiC powder (WC:Co:TiC = 6:2:2) as outer material and 304 stainless steel as core are compressed at room temperature and sintered at high temperature in a vacuum tube furnace by self-designed mold in the laboratory. The influence of sintering temperature on microstructure, diffusion of elements, hardness and wear resistance are studied by scanning electron microscope, hardness tester, and friction and wear tester. The results show that with the increase of sintering temperature, the number of micropores in WC-Co-TiC/304 stainless steel composites decreases, the mutual diffusion trend of Co and Ni increases, the Fe, Cr and W are slightly diffused, and Ti element has no obvious diffusion. With the increase of sintering temperature, the hardness increases and the wear resistance decreases of WC-Co-TiC/304 stainless steel composites. When the sintering temperature is 1310 °C, the hardness of WC-Co-TiC cemented
With the continuous development of science and technology, the increasingly severe service environment makes people put forward higher requirements for the performance of alloy steel. Tungsten has unique properties such as excellent strength, high density and good hardness, and its addition as an alloying element will change the properties of alloy steel. This paper aims to summarize the effect of the addition of tungsten on the microstructure and mechanical properties of alloy steel. The background of research and application of tungsten alloyed steel is presented initially. Then, the preparation methods of tungsten alloyed steel are described. Next, the effect of tungsten incorporation on the microstructure of alloy steel is reviewed. Finally, the effects of tungsten addition on the mechanical properties, corrosion resistance and hydrogen embrittlement resistance of the alloy steel are reviewed. This review provides an outlook on the development of tungsten alloyed steel, which will
Effective hardening depth (EHD) and surface hardness (SH) achieved by carburizing heat treatment play vital roles in guaranteeing the fatigue performance of heavy load carburized gears, which are often subjected to fatigue failure in the engineering practice. In this study, a strategy of combining the pre-shot peening process and subsequent carburizing heat treatment was proposed to improve the efficiency of carburizing heat treatment of AISI 9310 gear steel. Characterizations of hardness, material microstructure, surface roughness and micro-strain of treated roller samples were conducted with helps of a microhardness tester, optical microscopy, scanning electron microscope, white light interferometer and X-ray diffraction, respectively. The underlying mechanism was explored in terms of discovering the relationship between EHD and microstructure, plastic deformation, surface roughness. Results indicated that the efficiency of carburization heat treatment of AISI 9310 gear steel has bee