EVALUATION OF COATINGS TENDENCY TO THE PORES AND NON-METAL INCLUSIONS FORMATION IN A WELD

The task of welding steel elements painted with various coatings is found in a number of industries at the stages of factory assembly and installation of large-sized structures, as well as during repair and restoration work. The porosity of the welded metal is the most common defect in electric arc welding without removing the coating, and the tendency to pore formation is a normalized parameter in the certification of interoperable primers (EN ISO 17652-2: 2003). The studies carried out cover wide-spread polyacrylate, alkyd, epoxy, polyvinyl butyral primers in an extended working thicknesses range. In addition, the evaluation technique is used for zinc-filled and organosilicate protective coat-ings. Based on the study of the nonmetallic inclusions composition in a weld by energy dispersive X-ray spectroscopy and using a scanning electron microscope, the behavior features of the coatings de-struction products and their derivatives during physical and chemical transformations under welding are described. The technological features of welding without coating removing are noted: stability of the mode parameters, resistance to metal spraying and coating burnout activity in the areas adjacent to a weld.

Installation for producing of spherical metal powders for additive technologies

A unit was developed for the production of powders of various metals with a dispersion of 0.5÷100 mm of a spherical shape and a given particle size distribution. Keywords powder, metal, spraying, sphere, dispersion. [email protected]

Electromagnetic Shielding Performance of Carbon Black Mixed Concrete with Zn–Al Metal Thermal Spray Coating

The electromagnetic pulse (EMP) is a destructive phenomenon which harms the building, telecommunication, and IT based infrastructure. Thus, it is required to reduce the effect of EMP using shielding materials. In the present study, we have used different thickness of concrete walls by incorporating 1 and 5 wt% of carbon black, as well as 100 µm thick Zn–Al coating using the arc thermal metal spraying method (ATMSM). The EMP was evaluated using waveguide measurement fixture for shielding performance of the concrete wall in the range of 0.85 to 1 GHz frequency. The results reveal that the maximum value, i.e., 41.60 dB is shown by the 5-300-N specimen before application of Zn–Al coating where the thickness of concrete wall was 300 mm and 5% carbon black. However, once the 100 µm thick Zn–Al coating was applied on concrete specimen, this value was increased up to 89.75 dB. The increase in shielding values around 48 dB after using the Zn–Al coating is attributed to the reflection loss of the metal thermal spray coating. Thus, the Zn–Al coating can be used for EMP application instead of metallic plate.

Characterization of Cr2O3 Adhesion Properties by Destructive Testing in Accordance with the APS Metal Spraying Process Parameters

This paper aims to study the correlation between some parameters of the metalspraying by APS process and the level of chromium oxide (Cr2O3) adhesion to the base material. Among the properties of the layers deposited by APS are those of wear resistance. In the context of evaluating the coatings properties and understanding aspects related to the coat structure phenomena, the purpose of the experiment presented here is to characterize the adherence of thermal sprayed coating Cr2O3. Because, the main problem of metalspraying layers is adhesion to the base material, there were subjected to tensile testing 2 samples made by 1C45 steel, which were previously bonded with an epoxy glue. The adhesion of the deposited layer on the basic material is important for ensuring the quality of products. The results show that the quality of surfaces and the existence of accidental defects at the interface lead to a decrease of adherence.