Improvement of Heat Sink Performance Using Graphite and Graphene Coating

This experimental research depicts the role of coating hot surfaces by graphite and graphene on the process of heat dissipation from these hot surfaces. Three aluminum specimens have been prepared for test, one of theme is coated by graphite, another one by graphene a while the third is left free of coating for comparison purpose. Each specimen is tested separately in a home-made wind tunnel. A plate electrical heater is adhered on the bottom of the specimen to simulate the generated energy by a heat sink. A heat sink composed of high thermal conductivity was applied between the heater plate and the base plate of heat sink to reduce the contact resistance to heat flow. The experiments are conducted with four turbulent Reynolds number. The results reveal that the sample coated by graphene exhibits the best thermal dissipation while the uncoated specimen shows the worst thermal performance.

Study on Fatigue Life of Heat-treated Aluminium alloy coated with Castor oil.

This paper involves the study of fatigue life of coated aluminium alloy Al 7075-T651 that is heat-treated under 100oC soaked in castor oil for three days. The specimen after heat treatment is subjected to fatigue test using rotary bending machine for number of cycles to fail under cyclic load of 15kgf, 25Kgf, and 50kgf.The life of the specimen is found and compared with uncoated specimen and improved life in number of cycle is noticed. The crack propagation and its type is analysed using scanning electron microscope for knowing the point of fracture and its initiation to failure.

Electrochemical property analysis of SiO2-Al2O3-coated steel by electrochemical impedance spectroscopy

Purpose The purpose of this paper is to investigate the corrosion resistance of SiO2-Al2O3 coating on mild steel. Design/methodology/approach SiO2-Al2O3 was coated using sol-gel method, and electrochemical measurements were applied to assess the performance of the coated steel. Findings The main conclusion is that SiO2-Al2O3-coated specimens acquired a higher corrosion resistance than that of uncoated specimen. icorr values of the coated specimens were between 12 and 14 times smaller than those of uncoated specimen. The coated specimens exhibited a higher Rcor value at electrochemical impedance spectroscopy analysis. The high values of Rcor and low values of CPEdl observed within the SiO2-Al2O3-coated samples imply an improved anti-corrosion capability. Originality/value In this work, there are three points of originality. First, steel specimens were coated with ormosil-based solution by applying sol-gel dip coating method. Second, both SiO2 and Al2O3 coatings were applied simultaneously at a considerably low temperature, i.e. 200 °C. Finally, the performance of the coated materials against wet corrosion was improved significantly.

Chromia Evaporation of Ferritic Stainless Steel AISI430 Coated by (La,Sr)CrO3 Perovskite and Mn-Co Oxide Spinel

A ferritic stainless steel has been intensively studied for its potential in application as an interconnect for a solid oxide fuel cell (SOFC). However, at such a high operating temperature chromia in the gaseous phase can contaminate the cathode of the SOFC, and consequently the performance of the device degrades rapidly. To overcome this problem, two kind of ceramics, (La,Sr)CrO3 perovskite and Mn-Co oxide spinel were prepared as coatings on the stainless steel AISI 430 to investigate on chromia evaporation at 800°C. In this present work, the (La,Sr)CrO3 and Co-Mn layers were formed by a sol-gel dip coating and an electrodeposition technique, respectively. The coatings were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), rates of oxidation and rates of chromia evaporation. The coated specimens exhibited the protective behavior with a lower rate of oxidation, as well as a lower rate of chromium evaporation than the uncoated specimen both in the atmosphere of dry and humidified oxygen. But the reduction of the chromia evaporation rates of (La,Sr)CrO3 coatings was insignificant due to the presence of Cr2O3 phase in the coatings.

Determining Anisotropic Young’s Modulus of Ceramic Coatings by the Relative Method

Young’s moduli of coatings in the both perpendicular and horizontal directions were evaluated by the relative method, which are determined via establishing the relationship between the uncoated specimen and the coated specimen, with different coating positions during the loading tests. Compared with other traditional methods, the relative method is much simpler in both sample pretreatment and testing device. The validity and reliability of this method has been demonstrated by the beam specimens with CVD-SiC coatings, which will be applied to establish and improve a simple and reliable evaluation system for the anisotropy of coating modulus.

Ablation Property of the Plasma Sprayed NiCrAlY-ZrO2 Compound Coating on Stainless Steel Material

The NiCrAlY-ZrO2 anti-ablation compound coating was prepared on one surface of a 201stainless steel by plasma spraying, and the ablation property was studied by the cyclic ablation experiment. The morphology and XRD pattern of the NiCrAlY-ZrO2 coating were characterized by SEM and XRD methods before and after ablation on the high-temperature oxyacetylene flame. The results show a good adhesion between the coating and substrate. After the ablation at high temperature flame, the smoothness of the coating surface declined. The coating, under the oxyacetylene flame of 2800°C, can effectively improve the anti-ablation property of the substrate material, the mass loss for the coated sample is 1/4 of the uncoated specimen under the same number of ablation cycles.

Properties of Iron Tailing Coatings on Stainless Steel Substrate

Flame sprayed iron tailings coatings on the boiler steels are characterized before and after melting. The attempt has been made to investigate the microstructure, erosion resistant, wear resistant of the coated and melted samples. The techniques used are SEM and XRD. The results show that: Good adhesion between the coating and the substrate is caused by the formation of Al2SiO3 and (Cr, Fe)2O3at the interface of the coated specimen. The stainless steel substrate with ceramic coating has a higher erosiSubscript texton resistance than the uncoated specimen because the mixed powder changes to a glass-coating in the high temperature heat treatment, and a few mullite are formed. Mullite has the high hardness value that makes the hardness of the coating increased. The wear resistance of the coated samples is better than that of the uncoated samples because glass-coating is more smooth than the uncoated specimen and the mullite in the coating has the high hardness value that makes the hardness of the coating increased.

Properties of Ceramic Coatings on the Wall of Coke Oven

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.

Coating Evaluation Using Ultrasonic Wave Technology

The capability of Rayleigh wave to be used as a tool for the evaluation of CVD DLC coating layer has been presented in this paper. One uncoated specimen and two CVD DLC coated specimen has been used. The dispersion curves of group velocity of leaky Rayleigh wave were measured. The dispersion curve of uncoated specimen shows that the group velocities were same at different frequencies, as there is no coating layer affecting the group velocities at different frequencies. There are distinct different between ‘sound’ specimen and ‘bad bonding’ specimen as the ‘bad bonding’ specimen show unevenness on its dispersion curve.

Effect of HVOF Sprayed MCrAlY Coating on Thermomechanical and Isothermal Fatigue Life of Superalloy M963

A cast nickel based superalloy M963 was coated by high-velocity oxy-fuel (HVOF) spraying process. The effect of HVOF MCrAlY coating on thermo-mechanical fatigue (TMF) and isothermal fatigue (IF) in M963 was studied to understand fatigue life and failure mechanisms in coated and uncoated M963 alloy. Two types of TMF tests, i.e. in-phase (IP) and out-of-phase (OP), were performed in temperature range of 450~900°C, and IF tests were conducted at 900°C. It was found that the coating had a detrimental effect on fatigue life under OP TMF, while a beneficial effect of the coating existed under IP TMF and IF. Crack initiation time in the coated specimen was shorter than that in the uncoated specimen and the former’s crack density was higher than the latter’s one under OP TMF. The relationship of deformation and fracture response with fatigue life was discussed based on microscopic analysis.