Advanced Materials Research Vols. 189-193

Abstract: Al-8%Si alloy double-coating on Q235 steel were produced, Then the samples were executed diffusion at high temperatures protecting with flowing argon gas. Scanning electron microscope (SEM), optical microscope (OM), and energy dispersive X-ray spectroscope (EDS) were employed for microstructure observation of cross-sectional, surface and compositional analysis of coating. The diffusion mathematical model was established with the finite element method. The results show that good quality Al-8%Si coating is made; after heat-diffusion treatment, the new phases FeAl and Fe3Al presents; Silicon atoms in Al-8%Si alloy can hinder the diffusion of aluminum atoms into steel substrate at high temperature; Al-8%Si alloy double-coating sample’s high-temperature oxidation resistance is higher than Q235 steel. This material is hopefully used in the engine exhaust manifold.

Abstract: The influence of frictional wear characteristics were investigated under the Self-repairing Additive condition with different concentration by using MMU-5G end-face friction and wear testing machine. The surface images of friction pair and their chemical composition were detected by using SEM and EDS. The result indicates different concentration has a great influence on frictional wear characteristics of friction pair. The Self-repair coatings are formed on the 45#steel worn surface while nothing on the cast-iron worn surface, study considers that metallographic structure and mechanical performance of cast iron are the prime causation resulting in no Self-repair coatings. Self-repairing Additive of the right concentration has remarkable effect on antifriction and wearing of cast iron.

Abstract: TiAl-Cr alloy was prepared on surface of TiAl based alloy by plasma surface alloying technique. The wear resistance of the surface alloy was examined under various wear condition. During the room temperature ball-on-dic sliding test, the TiAl-Cr surface alloy showed reduced friction and improved wear resistance. For the 500°C sliding and room temperature fretting tests, the friction coefficient of TiAl-Cr surface alloy was a little higher than that of TiAl-based alloy, but the wear volume showed significant reducing, the wear resistance was improved obviously. The addition of chromium increases the strength and hardness of the TiAl-based alloy, and therefore the load bearing and anti-adhesion capacity of the surface were also enhanced, these were the main mechanisms for the improvement of wear resistance.

Abstract: In this work, the effect of plating temperature on the electroless plating rate and the properties of the electroless Ni-Cu-P deposits was studied. The corrosion resistance, hardness, surface morphology and components of the coating were studied by using electrochemical workstation, digital micro-hardness SEM and EDS. The results show that the optimum plating temperature is 75°C. The deposition rate, hardness and corrosion resistance are all good when the optimal temperature is 75°C. The adhesion between the deposits and the matrix is better. The deposits is smooth and uniformity, smooth by SEM. The deposit contains Ni 77.80%, Cu 7.68%, P 14.52% by the analyses of energy disperse X-ray.

Abstract: The photoaging of polyurethane coating based on TDI-TMP and N3390 was conducted though UV exposure. The properties of studied polyurethane coatings, such as film thickness loss, gloss loss, discoloration and ultraviolet absorbance were examined at some aging intervals. In addition, scanning electronic microscopy (SEM) and Fourier transform infra-red spectroscopy (FTIR) were used to measure the morphology and chemical change of coatings before and after exposed in a UV lamp chamber. It was found that the addition of N3390 had a significant effect on the discoloration of polyurethane coating, and coating without N3390 had greater degradation. The above results suggested that a mixed curing agent system with a mass ratio of TDI-TMP to N3390 between 5:5 and 3:7 be a possible substitute of pure N3390 for weather resistance PU coatings.

Abstract: Flame sprayed ceramic coatings on the wall of coke oven are characterized before and after melting. The attempt has been made to investigate thermal shock resistant, carbon deposit resistant, wear resistant of the coated and melted samples. The techniques used are SEM and XRD. The results show that: 1) Presence of quartz, corundum and mullite are identified in the surface of the coated specimen. Good adhesion between the coating and the substrate is caused by presence of quartz which is the same content as the substrate.2) The thermal shock resistance cycles of the coating samples are 15 ~ 30 times, but uncoated samples are only 1~2 times. The main reason is that he coating–substrate interface shows no gaps or cracks, and it has a characteristic feature of good adhesion between the coating and the substrate. 3) The wear resistance of the coated samples are better than that of the uncoated samples because glass-coating is more smooth than the uncoated specimen and the mullite and corundum in the coating have the high hardness value that makes the hardness of the coating increased.

Abstract: In this paper, the artificial UV accelerated aging test was used to investigate the effect of curing agents including TDI-TMP prepolymer, N75, N3390 and IPDI propylene acid resin on the photoaging of polyurethane (PU) coatings. The thickness and gloss loss, color difference, as well as UV absorption of PU coatings were measured during the UV exposure, meanwhile FTIR and SEM were utilized to monitor the chemical and mophological change after UV exposure. The TDI-TMP prepolymer coatings showed the worst aging resistance and whilst the results of N3390 coatings are relatively good.

Abstract: The siliconized layer on low silicon steel substrate was produced under pulse current conditions from KCl-NaCl-NaF-SiO₂ molten salt and the effects of frequency on the composition and microstructure were investigated. The results showed that at the same average current density and other experimental conditions, Si content in the surface and the layer thickness decreased with increasing frequency. Low pulse frequency (500 Hz) and high frequencies (1500, 2000Hz) produced coarse grain and bigger surface roughness. There was a flat fine grain structure and a relatively thick (30m) layer when the frequency was 1000Hz. However, the effect of pulse frequency on the structure of the layer was not obvious. The phase structure of the layer was composed of Fe₃Si with (110) preferred orientation at all experimental frequencies.

Abstract: This paper first elaborates the domestic and foreign study and applying current situation in terms of the concrete testing field regarding to acoustic emission technology, especially the study progress in the large dam concrete field. By improving the current test device and updating and reforming the measuring equipment, the task team introduces the acoustic emission testing system into the concrete double-K fracture parameter test. The new device can not only accurately control the loading velocity in the test, but also correctly judge the time and property of cracking, instability and damage of specimen. This paper establishes the acoustic emission criterion for concrete fracture according to the recognition features of acoustic emission of concrete in fracture critical state. The test result presents that the cracking time of specimen can be correctly judged by using feature parameters of acoustic emission, which properly matches the cracking time measured by the traditional strain method, and this judging is more direct and convenient for on-site operation, providing theoretical and technical support for application in the concrete fracture parameter test by acoustic emission technology.

Abstract: In order to calculate the fatigue life, lifting or unloading position, lifting weight and load mobile line of crane with automatic acquisition device were recorded on spot. Probability distribution model and its characteristic parameters of lifting weight and lifting or unloading position were analyzed with goodness of fit test. The random samples of the load spectrum parameters for the cumulative fatigue were also calculated with Latin Hypercube Sampling. Dynamic simulation model of crane metal structure was formed. Dynamic load function that dynamic load changed with time was also established, from which the stress spectrum through structural dynamics analysis in fatigue calculation point was acquired. Based on then above calculation, the remaining fatigue life of the prototype is 38 years.