| Nuclear energy is a new and clean energy, which is different from thermal power. The nuclear system need no require fuel storage、no waste site and so on during power generation process. Additionally, no harmful gas is produced. The development of nuclear energy plays a significant role in the strategic planning of our country. Due to the development of nuclear, it can drive the development of related industries and high-tech. Many components in nuclear system are operated in high temperature, high pressure and water environment, and the friction behavior of components must be considered in the design process. However, the traditional method of measuring static friction coefficient does not work in high temperature, high pressure and water environment. Besides, in order to measure the dynamic friction coefficient, a special holder need to be designed. Therefore, static and dynamic friction coefficient tests were carried out in high temperature, high pressure and water environment in this paper, and it can provide useful data for computing force in nuclear system.The static friction coefficient tests were carried out using a self-made wear tester in line and surface contact configuration. Moreover, the dynamic friction coefficient tests were carried out in line contact configuration after remoulding tester. In this paper, six friction pairs were selected, they are F6NM martensitic stainless steel against SA-336 Type 304H stainless steel, SA-508 Gr.3 Cl.1 low-alloy steel against 45 steel, SA-508 Gr.3 Cl.1 low-alloy steel against P460NH steel, SA-516 Gr.70 steel against 5454-H32 aluminum,45 steel against Q420B steel, and 45 steel against SA-533BCL.1 steel, respectively. After machined, all the samples were measured by a 3D/2D morphology analyzer in order to obtain the roughness. The aim of this paper is to assess the effect of temperatures, normal pressure, roughness and speed on static/dynamic friction coefficients. After tests, the wear volume of SA-516 Gr.70 steel and5454-H32 aluminum were measured to reveal the effect of time and normal pressure on wear. The conclusions were as following:(1) According to classical theory of friction and the actual working environment of nuclear power plants, a tester was developed for measuring static friction coefficients. The tests were in line and surface contact configuration using three contacting pairs. The tester can attain different experimental conditions (normal pressure fromlkN to 60kN, temperature RT to 350℃ in air, and temperature from RT to 90℃ in water). The results of this tester were similar to coefficient curve of classic friction, which proved its feasibility.(2) The static friction coefficient of all friction pairs increased with the increase of temperature. On the contrary, the temperature effect on dynamic friction coefficient was different. Due to different wear mechanism, with the increase of temperature, dynamic friction coefficient first increased then decreased for friction couples with higher stiffness. With the increasing temperature, it was easier for mating materials to adhere together, consequently higher static friction.(3) The static friction coefficient of F6NM martensitic stainless steel against SA-336 Type 304H stainless steel increased with the increase of roughness and stress, but dynamic friction coefficient was opposite. The static friction coefficient increased with the increase of normal pressure, because the actual contact area will not be enlarged under high normal pressure. The increase of normal pressure resulted in the increase of the shear force. Higher shear force induced more debris, which acted as solid lubrication. Consequent, the dynamic friction coefficients decreased. The increase of roughness resulted in the decrease of contact area and the increase of pressure. Therefore, roughness and normal pressure have the same effect on static/dynamic friction coefficients.(4) The static and dynamic friction coefficient of SA-516 Gr.70 steel and aluminum 5454-H32 friction all decreased with the increase of stress. The hardness of SA-516 Gr.70 steel is bigger than aluminum 5454-H32. The increase of pressure resulted in the increase of the real contact area, which resulted in increase of static friction coefficient. The increase of normal pressure resulted in the increase of the shear force. Higher shear force induced more debris, which acted as solid lubrication. Finally, the he dynamic friction coefficients decreased.(5) In the article, two speed were selected, e.g., e 1mm/s and 10mm/s. The results showed that speed has no effect on dynamic friction coefficient under the test parameters.(6) Under the same stress, the wear volume of SA-516 Gr.70 steel and aluminum 5454-H32 friction all increased with the increase of time, however, the wear rate decreased. At the beginning of the test, the material was easy to wear, then harder. The wear volume increased and then decreased with the increase of normal pressure. On the other hand, the wear rate decreased. With the increase of stress, the damage of specimens was severer. When the stress reached a special value, the main wear mechanism was adhesive wear. The transform layer attached to the wear surface prevented further aggravate wear. The increase rate of wear volume was less than the speed of stress with the increase of pressure, which resulted in the decrease of wear rate. |
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