Aneta Ziewiec

Microstructure of the Fe-Ni-P Melt-Spun Ribbons Produced from the Single-Chamber and from the Double-Chamber Crucibles

The aim of the work was to investigate the influence of the processing on the final microstructure of the melt-spun Ni-Fe-P ribbons. The melt-spinning was carried out in two ways. For the first one the alloy was molten in a simple single-chamber crucible and for the second one double-chamber crucible was used. The chemical composition of the alloy molten in the single chamber was Ni40Fe40P20. The two component melt-spinning was made starting from the Ni80P20 and Fe80P20 alloys. All of the three alloys were molten in titanium gettered argon atmosphere starting from 99.95 wt % Ni, 99.95 wt % Fe, Ni-P and Fe-P master alloys in the arc melting furnace. The alloys were melt-spun in helium. The phase composition and the microstructure of the melt-spun ribbons were investigated by X-ray diffraction (XRD), a transmission electron microscope (TEM), respectively. The fracture of the specimens were observed with use of scanning electron microscope (SEM). SEM observations of the fracture surfaces show different character of the fractured samples.

The role of hydrogen in weld cracking processes – a new look at the problem

Hydrogen’s effect on steel properties has already been described in many publications and monographs. Usually in these publications, only hydrogen’s effect on properties and cracking at near ambient temperatures and minus temperatures is analysed. For example, similar effects of hydrogen on properties and weld cracking are described in detail in Refs. 3–7. Until now, the common belief was that hydrogen causes:

Technology of welding and properties of welded joints of new bainitic and martensitic steels with creep-resistant steels

This paper shows the results of welding tests used so far on high-temperature creep resistant steels and new bainitic and martensitic steels. The positive results of this research allowed the elaboration of a welding procedure specification that was ultimately approved by TÜV. This then allowed the SEFAKO Company to attempt welding of the latest generation boiler steels for use under heavy conditions.

Influence of post-weld heat treatment (PWHT) on the structure and properties of welded joints of chromium–nickel stainless steel with soft martensite

This paper reviews the results of investigations on how post-weld heat treatment (PWHT) influences the hardness and microstructures of welded joints in stainless steel X3Cr-NiMo 13-4. It is known that welding leads to high segregation of components in the solidification process, which has an influence on phase transitions in PWHT. The investigated steel has a very narrow PWHT range, about 600–620°C, which provides optimum levels of hardness and toughness. Excessive annealing temperature leads to decreased toughness, which in turn causes exceeding of the Ac1 temperature in the segregation range, which then leads to increased ‘fresh’ martensite content.