Mechanical properties and residual stresses of friction stir welded and autogenous tungsten inert gas welded structural steel butt welds have been studied. Friction stir welding (FSW) of structural steel butt joints has been carried out by in-house prepared tungsten carbide tool with 20 mm/ min welding speed and 931 rpm tool rotation. Tungsten inert gas (TIG) welding of the butt joints was carried out with welding current, arc voltage and the welding speed of 140 amp, 12 V and 90 mm/min respectively. Residual stress measurement in the butt welds has been carried out in weld fusion zone and heat affected zone (HAZ) by using blind hole drilling method. The magnitude of longitudinal residual stress along the weld line of TIG welded joints were observed to be higher than friction stir welded joint. In both TIG and FSW joints, the nature of longitudinal stress in the base metal was observed to be compressive whereas in HAZ was observed to be tensile. It can be stated that butt welds produced with FSW process had residual stress much lower than the autogenous TIG welds.

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.

The article discusses tests concerning the assessment of the corrosion resistance, properties and the structure of TIG braze welded galvanised steel sheets. Test butt joints were made of 0.9 mm thick galvanised car body steel sheets DC04 (in accordance with EN 10130), using a robotic welding station and a CuSi3Mn1 braze (in accordance with PN-EN 13347:2003) wire having a diameter of 1.0 mm. The research-related tests aimed to optimise braze welding parameters and the width of the brazing gap. The test joints were subjected to visual tests, macro and microscopic metallographic tests, hardness measurements as well as tensile and bend tests. The corrosion resistance of the joints was identified using the galvanostatic method. The tests revealed that it is possible to obtain high quality joints made of galvanised car body steel sheets using the TIG braze welding process, the CuSi3Mn1 braze and a brazing gap, the width of which should be restricted within the range of 0.4 mm to 0.7 mm. In addition, the joints made using the aforesaid parameters are characterised by high mechanical properties. The minimum recommended heat input during process, indispensable for the obtainment of the appropriate spreadability of the weld deposit should be restricted within the range of 50 kJ/mm to 70 kJ/mm. At the same time, the aforesaid heat input ensures the minimum evaporation of zinc. Joints made using the TIG braze welding method are characterised by high resistance to electrochemical corrosion. The galvanostatic tests did not reveal any traces of corrosion in the joint area.

The article summarizes the theoretical knowledge from the field of brazing of graphitic cast iron, especially by means of conventional

flame brazing using a filler metal based on CuZn (CuZn40SnSi – brass alloy). The experimental part of the thesis presents the results of

performance assessment of brazed joints on other than CuZn basis using silicone (CuSi3Mn1) or aluminium bronze (CuAl10Fe). TIG

electrical arc was used as a source of heat to melt these filler materials. The results show satisfactory brazed joints with a CuAl10Fe filler

metal, while pre-heating is not necessary, which favours this method greatly while repairing sizeable castings. The technological procedure

recommends the use of AC current with an increased frequency and a modified balance between positive and negative electric arc polarity

to focus the heat on a filler metal without melting the base material. The suitability of the joint is evaluated on the basis of visual

inspection, mechanic and metallographic testing.

This article discusses the influence of Tungsten Inert Gas (TIG) surfacing of duplex cast steel on its hardness and structure. The samples of 24Cr-5Ni-2.5Mo ferritic-austenitic cast steel were subjected to single-overlay processes with the use of solid wire having the chemical composition similar to that of the duplex cast steel. As a result of the surfacing, the welds were obtained that had no welding imperfections with a smooth transition to the base material. In the test without the heat treatment, directly below the fusion line, we observe a ferrite band with a width of approximately 200 m without visible austenite areas. Some of the samples were then solution treated (1060°C). Both variants, without and after solution heat treatment, were subjected to testing. Significant changes in the microstructure of the joint were observed after the heat treatment process (heat affected zone and weld microstructure changes). In both areas, an increase in the austenite volume fraction after solution heat treatment was observed. Changes in the microhardness of the ferrite in the HAZ area directly below the fusion line were also observed.

The welding of nuclear grade P91 and P92 steel plate of thickness 5.2 mm were performed using the autogenous tungsten

inert gas (TIG) welding process. The welded joint of P91 and P92 steel plate were subjected to the varying post weld heat-treatment

(PWHT) including the post weld heat treatment (PWHT) and re-austenitizing based tempering (PWNT). A comparative study was

performed related to the microstructure evolution in fusion zone (FZ) of both the welded joint using the scanning electron microscope

and optical microscope in a different condition of heat treatment. The hardness test of the FZ for both joints was also conducted in

a different condition of heat treatment. P92 steel welded joint have observed the higher tendency of the δ ferrite formation that led

to the great variation in hardness of the P92 FZ. The homogeneous microstructure (absence of δ ferrite) and acceptable hardness

was observed after the PWNT treatment for both the welded joint.

The development of power industry obligates designers, materials engineers to create and implement new, advanced materials, in which Inconel 617 alloy is included. Nowadays, there are a lot of projects which describe microstructure and properties of Inconel 617 alloy. However, the welded joints from mentioned material is not yet fully discussed in the literature. The description of welded joints microstructure is a main knowledge source for designers, constructors and welding engineers in estimating durability process and degradation assessment for elements and devices with welds of Inconel 617 alloy. This paper presents the analysis and assessment of advanced nickel alloy welded joints, which have been done by tungsten inert gas (TIG). Investigations have included analysis made by light microscope and scanning electron microscope. The disclosed precipitates were identified with Energy Dispersive Spectroscopy (EDS) microanalysis, then it were done X-Ray Diffraction (XRD) phases analysis. To confirm the obtained results, a scanning-transmission electron microscope (STEM) analysis was also performed.

The purpose of the article was to create a comprehensive procedure for revealing the Inconel 617 alloy structure. The methodology presented in this article will be in future a great help for constructors, material specialists and welding engineers in assessing the structure and durability of the Inconel 617 alloy.

Titanium and its alloys have significant uses in the biomedical, chemical, and aerospace industries. In this article, the current and gas flow rates were varied using Taguchi’s experiment design. The mechanical properties of the welded joint made using tungsten inert gas (TIG) welding and Ti6Al4V ELI as filler metal was characterized using the microstructure, microhardness, and tensile strength. The joint was classified into three regions, namely, fusion zone (FZ), heat affected zone (HAZ), and base metal (BM). Results show martensitic microstructure within the fusion zone (FZ) and the heat affected zone (HAZ), which resulted in an increased hardness within the fusion and heat affected zone.