Papers by Keyword: Silding Wear

Abstract: Sliding wear mechanisms of the solution treated 18Cr-18Mn-2Mo-0.9N high nitrogen steel (HNS) were studied. Room-temperature dry sliding wear tests of the steel were carried out at various applied loads to explore the mechanism as a function of the load. The wear rate of the steel increased with the increase of the load; however, the increase rate was not constant. The rate increased slowly at low loads, rapidly at intermediate loads, and finally, the increase-rate became low again at high loads. Worn surfaces, their cross sections, and wear debris were examined, and phases of the heat-treated HNS as well as the wear debris were identified to find out the mechanism. The wear of the steel was found to be controlled by the tribo-oxidation, strain-induced phase transformation, and reverse transformation due to temperature rise on a wearing surface. The influence of each mechanism on the rate varied depending on the magnitude of the applied load.

Abstract: In the present work, the wear behaviour of coatings produced on Ti-6Al-4V alloy by micro-arc oxidation method was studied. The wear tests were performed using a pin-on-disc wear machine under dry sliding conditions. It is found that the MAO coating can efficiently improve the wear-resistant performance of Ti alloy in the test range of this paper. The coated samples demonstrated wear rates up to 5-12 times lower than that of the uncoated substrates tested. The wear behaviours are deeply characterized by the variations of coating structure and composition.

Abstract: Room-temperature dry sliding wear behavior of hot-pressure sintered monolithic Co, Co- 20 wt.% CuSn and Co-20 wt.% WC composites were investigated. Wear tests of the materials were carried out using a pin-on-disk wear tester at various loads of 10N-100N under a constant sliding speed condition of 0.38m/s against glass (83% SiO2) beads. Sliding distances were varied with a range of 100m-600m. A scanning electron microscopy was used to examine worn surfaces, cross sections, and wear debris. X-ray diffraction (XRD) was utilized to identify phases of the specimen and wear debris. All specimens exhibited low friction coefficients ranging from 0.12 to 0.4. The sintered Co exhibited distinctive wear that was characterized by shallow dug canals on worn surface, a very thin detaching surface layer, and fine debris. Thermal transformation of the Co specimen from ε (hcp) phase to α (fcc) phase occurred during the wear of the Co, which was inferred from XRD analysis of the wear debris. The transformation was suggested to cause the thin detaching surface layer and the fine wear debris of the sintered Co. The wear of the Co-CuSn composite proceeded by shear deformation of the CuSn particles, while WC particles of the Co-WC composite sustained most of the applied load, which resulted in the low wear rate with fine wear debris of the Co-WC composite.

Abstract: Effect of phase transformation and grain-size variation
of hot-pressed cobalt on its dry sliding wear was investigated. The sintered cobalt specimens were heat treated under different conditions and their tribological characteristics were examined. The sliding wear test was carried out against glass (83% SiO2) beads at 100N load using a pin-on-disk wear tester. A constant sliding speed of 0.38m/s and sliding distance of 600m were adapted. Worn surfaces, cross sections, and wear debris were examined by a scanning electron microscopy (SEM). X-ray diffraction (XRD) was utilized to identify phases of the specimen and wear debris. The cobalt specimens exhibited low friction coefficients of around 0.2. Thermal transformation of the cobalt from the hcp ε phase to the γ (fcc) phase during the wear was detected, which was deduced as a wear mechanism of the sintered cobalt. Typical wear characteristics of the cobalt including a thin detaching surface layer and fine wear debris were explained by the transformation. A correlationship between the grain size and the transformation was also explored.

Abstract: By means of a vacuum induction furnace, Cu-Ag-Cr alloy were produced. The wear property and mechanism of Cu-Ag-Cr alloy are studied, and its property was compared with a Cu-Ag alloy. The microstructure of the Cu-Ag-Cr alloy before wear tests was analyzed by transmission electron microscopy. Worn surfaces of the Cu-Ag-Cr alloy were analyzed by scanning electron microscope (SEM) and energy dispersive X-ray spectrum (EDS). Wear tests were conducted under laboratory with a special sliding wear apparatus that simulated the tribological conditions of sliding current collectors on contact wires, and alloy wire was slid against a copper-based powder metallurgy strip under unlubricated conditions. The results show that the wear rate of Cu-Ag-Cr alloy increase with the increase in the sliding speed and the sliding distance. Adhesive wear, abrasive wear and electrical erosion wear are the dominant mechanisms under the electrical current sliding processes. At lower sliding speed, adhesives wear and abrasive wear are the major wear damage, while electrical erosion wear and adhesive wear are the major at higher sliding speed. Under the same conditions, the wear resistance of the Cu-Ag-Cr alloy is 2~3 times of the Cu-Ag alloy.

Abstract: Surface alloys with composition ranging from 10 to 20% Cr were produced by laser surface alloying. Their microstructure consists of faceted plate-like Al4Cr intermetallic compound particles dispersed in a matrix of α-Al solid solution. During remelting, heterogeneous nucleation of eutectic Al7Cr/α-Al occurred in the undercooled liquid ahead of the columnar solid-liquid interface, followed by equiaxial solidification, resulting in a microstructure formed of equiaxed cells. Al-Cr alloys present Young’s modulus and hardness values that increase with increasing volume fraction of intermetallic compounds. Wear resistance, measured in dry sliding conditions, increases with increasing load due to the protective effect of a stable mechanically mixed layer that forms at the surface of the samples and the steel counterbody. Alloys formed of equiaxed eutectic cells provide better wear resistance than those formed of large plate-like particles since a thinner, more stable and harder mechanically mixed layer is formed, which offers best protection against wear.

Abstract: Wear damage of steam generator tubes for nuclear power plants can cause the leakage of radioactive substances. Therefore, the evaluation of integrity and safety for tubes is very important from the viewpoint of nuclear ecocide. In the present study, to investigate the wear properties of Inconel 600 and 690 steam generator tube materials mated with 409 stainless steel commonly used as support plate, sliding wear tests were performed with increasing sliding distance in air and in elevated temperature water environment, respectively. The wear volume of tube materials was less than those of supports under all conditions. There were no significant differences in the wear behavior for the Inconel 600 and 690 tubes, independently of the testing environment.

Abstract: A new iron-based wear resistance alloy was developed to replace the Co-containing Stellite 6 alloys in nuclear power industry. The effect of B addition on the wear resistance was investigated. Sliding wear tests of Fe-Cr-C-Si-xB (x = 0.0, 0.3, 0.6, 1.0 and 2.0 wt%) alloys were performed in air at the room temperature under a contact stress of 103 MPa. Low-boron alloys containing less than 0.6 wt% boron showed an excellent wear resistance than any other tested alloys. The improvement was associated with the matrix hardening by promotion of the γ→α′straininduced martensitic transformation occurring during the wear test. However, the alloys containing more than 1.0 wt% boron showed slightly increased wear loss compared to the low-boron alloys because of the absence of the strain-induced martensitic transformation and the presence of the brittle FeB particles, aiding crack initiation.

Abstract: Wear damage of steam generator tubes of nuclear power plants can cause leakage of radioactive substances. So the evaluation of tubes’ integrity is very important from the viewpoint of nuclear ecocide. In the present study, sliding wear behaviors of Inconel 600 and 690 steam generator tube materials mated with 409 stainless steel commonly used as the support plate were investigated at room temperature in an air environment. For more precise prediction of wear behaviors of steam generator tubes, Archard equation was modified, and the modified wear coefficients were estimated as a function of sliding distance. When using the modified Archard equation, the reliabilities for prediction of wear behavior of Inconel 600 and 690 mated with 409 stainless steel increased from 71.8% to 83.8% and from 60.2% to 85.2%, respectively.