Papers by Author: Janusz Adamiec

Abstract: Generally, nickel superalloy Inconel 625 is good weldability. However, it should be kept in mind his tendency to hot cracking during welding. Gamma matrix is strengthening by the alloying elements chromium, titanium, niobium. These elements favour the formation of carbides and intermetallic compounds that may cause embrittlement and hot cracking in a welded joint. Based on research the system Gleeble 3800 and transvarestraint test appointed criterion for susceptibility to hot cracking and high embrittlement temperature range (HTBR). Analysis of results allowed for evaluation of hot cracking structural mechanism of welded joints Inconel 625.

Abstract: The article presents the course and the results of research on comparison of material and technological welding conditions of EN AW 6082 aluminium alloy using low energy (CMT) and pulsed current (MIG-Pulse) welding methods, as well as discusses the properties of welded joints and the application fields of modern low energy welding devices for joining thin aluminium sheets.

Abstract: The article presents the course and the results of research on welding conditions and tendency of hot cracking occurrence connected with MIG (CMT or Pulse) welding method choice. EN AW 6082 alloy is considered hard-to-weld by using conventional arc welding processes (MIG-Pulse) due to the heat sensitivity and the tendency to hot cracking in the thin walled joints (weld, HAZ). MIG low energy method (CMT) was developed inter alia to solve this problem.

Abstract: The WE43 cast magnesium alloy is characterized by high development prospects due to its strength properties and maximum operating temperature of up to 250°C. It is used in the automotive and aircraft industries for engine, hull and gear parts. These are mainly individual or low-volume large-size casts, which in the casting process may display some defects in the form of misruns, shrinkage porosities and cracks. These defects are repaired with the application of welding technologies, which are also used to joint castings into structures and to repair castings after operation. The weld joint is an integral part of the structure. Therefore, it decides on the properties of the entire structure. It is important to get to know the microstructure and properties of magnesium alloy weld joints, and in particular those of the fusion weld. In this paper stability of the structure of WE43 cast magnesium alloy welded joint was researched.

Abstract: T23 is modern bainitic steel designed for use in supercritical boilers. According to producer’s data weldability of this steel is good enough to avoid post-weld heat treatment. However, some of the T23 weld joints in as-welded condition have not met the minimal ductility requirement. The impact test revealed significant differences between the joints in as-welded and heat treated condition. Metallographic and fractographic examinations have been conducted in order to explain those differences. The specimens with low impact strength were characterized by brittle fracture and non-tempered martensite presence in weld metal. It was concluded that avoiding formation of disadvantageous structure in weld metal requires conducting of post weld heat treatment or applying multi-pass welding technique with annealing run.

Abstract: Defining the susceptibility to hot cracking of Inconel 617 alloy welds is essential for assessment welding and pad welding technology. Because of that technological transvarestraint test was performed in the study. Test simulates strains that form in the material during welding. Transvarestraint test enables the assessment of susceptibility to hot cracking and resistance to hot cracking characterized by cracking threshold (ε_p) and critical strain speed (CSS). Performed investigations enabled to characterize the phenomena occurring in Inconel 617 during welds crystallization, which are important for engineers selecting the joining technology of Inconel 617.

Abstract: One of the most advanced manufacturing technologies is laser welding. Due to the limited power of the beam, the difficulty of precise preparation of the joint and the possibility of hardening in a narrow heat affected zone laser welding is used only for basic low carbon and low alloy steels. In this work the effects of autogenous weld parameters on microstructure and properties of the Inconel 617 alloy were studied. For this purpose the technological test of laser autogenous weld was performed.

Abstract: 7CrMoVTiB10-10 (T24) steel was designed for high temperature applications, especially for water wall panels in modern supercritical coal-fired boilers. However, welding of T24 steel caused many problems due to its cracking susceptibility. In the present paper the causes of T24 steel weld joints cracking have been discussed. Microstructural and fractographic analysis of weld joint were conducted and hardness was measured. It was found that the main causes of crack’s formation in weld metal are hot cracking susceptibility of T24, high deformation during welding process and weld metals’ hardenability. The mechanism of cracking was determined. It was concluded that cracks had been initiated in high temperature brittleness range, then propagated through the weld metal in transverse direction as the cold cracks. The reduction of weld metal’s ductility was due to too high cooling rate and excessive hardening of weld metal in relation to base metal.

Abstract: Welding and pad welding are widely used methods of repair and regeneration of defective magnesium alloys castings. AZ91 is one of the most popular magnesium alloys used at temperature up to 120°C. Therefore there is need to study the influence of welding and elevated temperature exposure on the microstructure and properties of AZ91 weld joints. This paper discusses microstructural stability of AZ91 gas tungsten arc weld joint in T6 condition (solution treated and aged). In order to examine the weld joints microstructural stability, the long-term annealing has been carried out at 120°C. Hardness of the base metal and fusion weld was measured after 250, 500, 750 and 1000h exposure respectively. Additionally, the base metals and the welds microstructure after 1000h annealing was investigated. Both in the base metal and in the weld, long-term annealing caused decrease in the intermetallic phases volume fraction. However, neither phase composition nor hardness of the weld joint were influenced by the heat treatment. Based on these results, it could be stated that the microstructure of investigated weld joint is stable at working temperature.

Abstract: Magnesium alloys of Mg-Zn-RE-Zr group are characterized by creep resistance up to 250°C, good castability, absence of the microporosity and gas corrosion resistance. Defect of these alloys are low mechanical properties at ambient temperature. Magnesium alloys are used in the automotive, aerospace and defense industries, mainly as gravitational casts to sand moulds or die-casting. Casting defects often appear in these casts (misruns, micro-shrinkage, cracks), especially for large-size castings. The welding technologies are most often applicable to repair of casts, mainly non-consumable electrode welding in the inert-gas cover. Welded joints made of magnesium alloys should have properties at least the same as the ready cast, in particular it should ensure stability of the structure and properties of all welded joint in working temperature. In the literature there is a lack of information about stability and properties of welded joints of Mg-4E-3Zn (EZ33A-T5 acc. to ASTM B80) alloy castings. In research work determined the structure of welded joints of Mg-4RE-3Zn alloy casting after stress-relief annealing and defined changes of structure and properties during long-term annealing at the temperature of 250°C. It was found that the structure of welded joint of casting alloy Mg-4RE-3Zn is stable at the temperature of 250°C through at least 1000 hours. The hardness of tested joints equal 80 HV. Therefore welding technologies can be used for repair of magnesium alloy casts with addition of zinc and rare earth elements.