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Attempts to Modify Austenitic Steel with Carbon Nanotubes

Górka Jacek, Kik Tomasz, Burda Michal

Archives of Metallurgy and Materials

2022

Vol. 67, iss. 1

349--356

In this work, research on influence of multiwalled carbon nanotubes (MWCNTs), produced in Catalic Chemical Carbon Vapor Deposition, NANOCYLTM NC7000CNTs on a structure and properties of AISI 301 steel remelted by TIG arc. In the assessment of influence a type of carbon on properties and structure of austenitic steel, as a carbon filler was use also carburizer. In the specimens (AISI 301 plates) with dimensions 155×60×7 [mm] were drilled holes with 1.3 mm diameter and placed 0.5 mm under specimen surface. Next, to the drilled holes was implemented CNTs, carburizer and mixture of these both powders. Prepared specimens were remelted by TIG method on the CASTOTIG 2200 power source with 2.4 mm tungsten thoriated electrode with parameters sets for obtain 3.0 mm penetration depth. Remelted specimens were cut into the half of the welds distance and prepared for metallographic examinations. Cross sections of the specimens were tested on classical metallography microscopes, hardness tests, SEM analyses (on JEOL 5800 LV SEM EDX equipment) and phase identification by X-ray phase analysis on Philips APD X’Pert PW 3020 diffractometer. Hardness analysis indicates about 25% increase of hardness in the remelted area when the CTNs are used. In the specimens with carburizer there is no significant changes. SEM analyses of remelted areas on AISI 301 specimens modificated with CNTs, indicates that dark areas, initially interpret as one of the phase (based on optical microscope) is finally densely packed bladders with dimensions from 50 nm up to a few µm. These bladders are not present in the specimens with carburizer filler. High resolution scanning microscopy allow to observe in the this area protruding, longitudinal particles with 100-300 nm length. For identification of this phase, X-ray analysis was done. But very small dimensions of used CNTs (diameters about 9,5 nm), random orientation and small weight amount can make difficult or impossible to CNTs detection during XRD tests. It means that it is not possible to clearly determine nature of particles filling the cavities, it is only possible to suppose that they are CNTs beams with nanoparticles comes from their disintegration. Results of the researches indicates, that fill in the weld pool with different form of carbon (CNTs and carburizer) it is possible to achieve remelted beads with different structure and hardness distribution. It confirms validity of the research continuation with CNTs as a modifier of steels and also other metals and theirs alloys.

Induction and electric arc-based remelting of thermally sprayed layers - overview

Węglowski Marek St., Jachym Robert, Krasnowski Krzysztof, Kwieciński Krzysztof, Pikuła Janusz

Biuletyn Instytutu Spawalnictwa w Gliwicach

2021

Vol. 65, No. 1

7--21

In many cases, the technology enabling the melting of thermally sprayed layers has no alternative. High-performance thermal spraying processes make it possible to obtain densely sprayed layers. However, previous research revealed that sprayed layers are characterised by porosity and numerous material imperfec¬tions. The above-named situation results from the specific manner of layer appli¬cation. The article overviews induction and arc-based technologies enabling the melting of sprayed layers as well as discusses possible post-spray imperfections.

Technologia przetapiania warstw natryskiwanych cieplnie w wielu przypadkach nie ma alternatywy. Procesy natryskiwania cieplnego są wysokowydajnymi procesami umożliwiającymi uzyskanie zwartych warstw natryskiwanych. Jednak przeprowadzone do tej pory badania wykazały, że warstwy natryskiwane charakteryzują się porowatością oraz licznymi niezgodnościami spawalniczymi. Jest to związane ze specyfiką nakładania warstw metodą termiczną. W pracy przedstawiono przegląd technologii przetapiania warstw natryskiwanych wykorzystujących metodą indukcyjną i łukowe. Omówiono również niezgodności spawalnicze, jakie mogą występować w warstwach po natryskiwaniu.