Volume 3 Issue 2
Authors: Jie Yang; Jinsheng Liu; Yuejin Ma; Jianguo Zhao; Jianchang Li; Jianjun Hao
Abstract: Wear is one of the three failure modes in materials, causing huge economic losses each year, and making research on wear resistance of great significance. The life of agricultural tools is significantly shortened by wear problems. However, due to the structure and performance needs of their materials, they may be unable to meet the requirements of agricultural production and costs would be extremely high if all agricultural tools were made of high strength, high hardness materials. In materials manufacturing and repairing processes, plasma surface welding is a commonly-used technology. In order to improve the wear resistance of a material as a whole, plasma-welding surface hardening technology was used by preparing Fe90 composite coatings on an ordinary carbon steel Q235 matrix. This coating ensured the toughness of the base material and improved the wear resistance of the surface, offering both economic and practical value. In this paper, through orthogonal testing and variance analysis, Fe90 composite coatings were prepared on ordinary carbon steel Q235 matrix using plasma welding systems, an MH-6 micro hardness tester, a HSR-2M reciprocating friction and wear testing machine, and scanning electron microscopy (SEM). The results demonstrated the effects of the current, plasma gas flow rate, powder feed rate, and welding speed on the performance of the coating; the optimal process parameters were obtained and then verified. The welding current was 200 A, powder feeding rate was 16 g/min, plasma gas flow rate was 2.0 L/min, and welding speed was 600 mm/min. Under the optimal process parameters, specimen #10 was obtained and its performance was verified. The wear resistance and hardness of specimen #10 was greatly improved, which proved the process would result in the extended life of agricultural tools.
Keywords: Plasma Welding; Composite Coating; Fe90; Wear Resistance; Micro-Hardness
Authors: Sebasti?o Cardoso; Ezio Castejon Garcia; Demétrio Bastos Netto
Abstract: In the last century, the technological development of flow machines has separated them into two distinct categories,: thermal machines and fluid machines. More recently, some researchers have contradicted traditional methods and have begun to invest time and money in the development of impulse machines, including Pelton turbines, to operate with compressible fluids. These machines are intended for use with incompressible fluids, however, in certain circumstances this equipment can be used to transform a portion of the energy content of compressible fluid into mechanical energy. The first difficulty is to transform thermal energy of the working fluid into kinetic energy without significant energy dissipation. Next, depending on the potential energy of the working fluid, it is necessary to use more than one machine in series to transform larger quantities of thermal energy into mechanical energy. Finally, a careful analysis of these machines operating with compressible fluids demonstrates that they cannot compete with reaction machines at low thermal efficiency. There remains an academic objective to disseminate traditional concepts of fluid machines, which are not always observed by directors and managers of companies, thus avoiding unnecessary expenses with the use and adaptation of compressible fluids in impulse machines.
Keywords: Energy; Thermal Machine; Impulse; Efficiency