An experimental investigation of the effect of coating on heat transfer during quenching

The work is aimed at studying the effect of galvanic nickel coating of a stainless steel cylinder on the quenching. In order to compare the results, the polished stainless steel cylinder was used as a sample. In addition, the influence of the formation of an oxide layer on the cooling process was studied. The experiments were carried out in water and ethanol with different subcoolings. The oxidized porous nickel coating led to increasing of the transition temperature from stable film boiling to intensive boiling regime. It was especially noticeable for cooling in water at high subcooling due to the higher cooling intensity caused by vapour layer thinning.

TOWEL DRYER AS AN ELEMENT OF THE MODERN HEAT SUPPLY SYSTEM

The operating conditions of the water-type towel dryer made of polished stainless steel AISI 304 are established, the declared capacity of towel dryers of almost the same design of different manufacturers is compared and a significant discrepancy is revealed; analyzed four methods for determining the nominal heat output of the towel dryer, taking into account the forced movement of the coolant inside the towel dryer, free or forced air movement near the surface of the towel dryer under different boundary conditions in compliance with regulations; modeling of towel dryer operation by means of Flow Simulation software module in SolidWorks; he influence of uncertainty of degree of blackness of a towel dryer surface on nominal thermal power of a towel dryer is investigated; influence of speed of washing of a heat exchange surface of a towel dryer by air on its thermal power is estimated, the received results of researches by four methods are analyzed.

Effect of Surface Pre-Treatment on Adhesive Strength of Multi-Component Vacuum-Arc Coatings

The results of investigations of multi-component nanostructured coatings of (TiAlSiY)N/CrN type are presented. The influence of different variants of substrate surface pretreatment on adhesive strength and hardness of coatings was studied. Pre-treatment of samples was carried out in plasma of two-stage gas discharge according to various technological schemes. Except for ion-plasma purification, some samples were pretreated with a sublayer of chromium within 5 minutes. The coatings were formed by a vacuum-arc deposition method at simultaneous spraying of two cathode targets. The first cathode is made of chromium, and the second cathode is made of multicomponent Ti - Al - Si - Y alloy obtained by vacuum-arc remelting of powder mixture of the mentioned elements. The coatings were deposited on polished stainless-steel substrates at negative 280 V bias potential. The geometry of the unit and its elements, as well as technological characteristics of the processes of evaporation-condensation were selected so that at a speed of rotation of samples 8 revolutions per minute the formation of the coating with a total thickness of about 9.0 microns occurred in approximately 60 minutes. The analysis of the composition of the coatings shows that the content of elements in the coating differs greatly from the content of elements in the sprayed cathodes. The X-ray diffractometry has shown that all deposition modes are characterized by the formation of phases with cubic (fcc) crystal lattice in both phase layers of multilayer coatings. In the layers formed at spraying of TiAlSiY alloy, a multi-element disordered solid solution (TiAlSiY)N with a crystal lattice of NaCl type and a lattice parameter of 0.4241 nm, as well as chromium mononitride CrN with a lattice parameter of 0.4161 nm, is determined. It has been established that preliminary formation of a chromium sublayer on the substrate leads to significant changes in adhesive strength of multi-component coatings compared to coatings without a sublayer.

Effect of Surface Modification on the Wettability and Static Coefficient-of-Friction between Steel and Ice

The effect of surface topography in combination with chemical composition on hydrophobicity and static coefficient-of-friction between steel and ice was studied. Polished stainless steel blocks were etched to introduce a roughness, and further treated with octadecanethiol. Carbon rich inclusions, identified by energy-dispersive X-ray spectroscopy, and scratches acted as the exposure centers to promote etching. Due to heterogeneities in steel, rounded cavities and parallel troughs were found on the surface after etching. Etched blocks with a lowered surface energy were studied under various ambient conditions to determine the influence of ice temperature and humidity on the static coefficient-of-friction. Blocks modified with octadecanethiol showed improved hydrophobicity. Warmer ice conditions led to a lower friction, regardless of the surface modification.

Friction and Slip Property Investigation of Nanostructured Metal Surface Coatings

In this study authors tests whether on inclined plane principle based simple experimental slip property estimation device which is modified with optical sensors for sample sliding time measurements can be effectively used for surface static sliding friction coefficient (COF) and dynamic slip property investigation. Parameters measured with the device allows to compare how different types of surface treatments (including nanostructured coatings) influence surface tribological parameters thus allowing to determine most efficient treatment technology. In order to verify slip property estimation device effectiveness in real life situation prototype was fabricated and experiments with 5 samples (1 polished stainless steel sample and 4 titanium-containing nanocoatings sputtered on same polished stainless steel substrates) were formed. Collected experiment data approved that such device can be effectively used for both COF and dynamic slip property investigation.

Characterisation of organic contaminants in the CLOUD chamber at CERN

The CLOUD experiment (Cosmics Leaving OUtdoor Droplets) investigates the nucleation of new particles and how this process is influenced by galactic cosmic rays in an electro-polished, stainless-steel environmental chamber at CERN (European Organization for Nuclear Research). Since volatile organic compounds (VOCs) can act as precursor gases for nucleation and growth of particles, great efforts have been made to keep their unwanted background levels as low as possible and to quantify them. In order to be able to measure a great set of VOCs simultaneously in the low parts per trillion (pptv) range, proton-transfer-reaction mass spectrometry (PTR-MS) was used. Initially the total VOC background concentration strongly correlated with ozone in the chamber and ranged from 0.1 to 7 parts per billion (ppbv). Plastic used as sealing material in the ozone generator was found to be a major VOC source. Especially oxygen-containing VOCs were generated together with ozone. These parts were replaced by stainless steel from CLOUD4 (June 2011) on, which strongly reduced the total VOC background. An additional ozone induced VOC source is surface assisted reactions at the electropolished stainless steel walls. The change in relative humidity (RH) from very dry to humid conditions increases background VOCs released from the chamber walls. This effect is especially pronounced when the RH is increased for the first time in a campaign. Also the dead volume of inlet tubes for trace gases that were not continuously flushed were found to be a short but strong VOC contamination source. For the later CLOUD campaigns lower ozone levels (below 100 ppbv) were used. During these conditions the total VOC contamination was usually below 1 ppbv and therewith considerably cleaner than a comparable Teflon chamber. On average more than 80% of the total VOCs are coming from only 5 exact masses (tentatively assigned as formaldehyde, acetaldehyde, acetone, formic acid, and acetic acid), which have a rather high vapour pressure and are therefore not important for nucleation and growth of particles.