Crystallization process of nickel-based amorphous alloys

IOP Conf. Ser.: Mater. Sci. Eng.

Fedotov

Сучков

et al. 2016

Abstract. Nanocrystalline ribbon filler metal-alloys of system Ni-Cr-Si-Be are produced by the rapidly quenching of the melt method. By these filler metals carried out hight temperature vacuum brazing of austenitic steels (12Kh18N10T and Kh18N8G2) and austenitic-ferritic class EI-811 (12Kh21N5T). The basic laws of structure-phase state foundation of brazed joints are determined, features of the interaction of the molten filler metal to the brazed materials are identified, the optimal temperature and time parameters of the brazing process are determined. IntroductionNowadays, brazing alloys containing boron are widely used for connecting stainless steels. One of the major problems in the application of boron filler metals is formation of heterogeneities in the brazed seam and heat affected zone, [1] which can negatively effect on the performance characteristics of the brazed joints and even cause destruction, as they adversely affect its fatigue strength and corrosion resistance [2]. Reducing the mass percentage of boron in the composition of the filler metal does not completely solve the problem. Therefore, new brazing alloys that do not contain boron on the basis of Ni-Cr-Si-Be for brazing stainless steels austenitic and austenitic-ferritic class are developing now.The requirements for strength properties and technology for preparing compounds of corrosion resistant steels are constantly increasing with the development of aerospace technology, the creation of advanced missile, space and aircraft design and manufacture of cellular or lattice panels and plate heat exchangers. Increasing the strength of connections can be achieved through the technological solutions or the use of new materials.The brazing has received a significant development among the methods of creating a permanently connection, which widely used in mechanical engineering. The use of brazing allows provides the compounds that can withstand high temperatures, mechanical stress and the effect of the active media for a long time without significant deterioration of their properties [3]. Therefore, the actual problem is to improve the mechanical properties of brazed joints by optimizing of structures and the development of new filler metals, improving their properties and technological modes of brazing.Nowadays rapidly quenched filler metals is widely apply. They are used in powder form or in the form of a ribbon with thickness of 20 ... 80 µm. This is a special category of filler metals, which represent a new class of advanced materials [4]. Such alloys produced ultrarapid quenching technique that gives certain advantages in the process of melting and interaction of the melt with brazed materials. It improves the quality of brazing, reduces the amount of defects and the formation of intermetallics in the brazed joints [5].

Section: Resultsmentioning

confidence: 99%

The use of Ni-Cr-Si-Be filler metals for brazing of stainless steels

IOP Conf. Ser.: Mater. Sci. Eng.

Fedotov

Сучков

et al. 2016

“…The phase composition and temperature of the phase transformations of considered nickel alloy have been rigorously studied [16,17]. This brazing alloy melts at 980-1035°С.…”

Section: Brazing Specimensmentioning

confidence: 99%

Effect of high-temperature brazing with a nickel-based STEMET 1301A brazing alloy on the unbrazing temperature of 12Kh18N10T steel joints

Int J Adv Manuf Technol

Krasnova

Penyaz

et al. 2020

The challenges facing the creation of brazed joints of 12Kh18N10T (AISI 321) austenitic stainless steel with high unbrazing temperatures for extreme working conditions in aerospace appliances are considered in this study. An amorphous-nanocrystalline nickel-based foil, Ni-7Cr-4.5Si-3.5Fe-2.6B, wt.%, is used for brazing the steel. Experiments on brazing regimes with various temperatures (1070-1160°С) and times of exposition (15-80 min) are carried out. The formation of Ni-based solid solutions with different Cr, Fe, Mn, Si, and Ti contents in the brazed seam is detected for all brazing regimes. Using Thermo-Calc software, the liquidus temperature located in a range between 1268 and 1388°С is calculated. To verify the calculated values, the unbrazing temperature is experimentally determined for specimens, with a composition of the solid solutions, formed in the center of the brazed seam during brazing at 1160°С/15 min, 1070°С/15, and 1160°С/80 min. The experimental results deviate from values computed by Thermo-Calc by no more than 54°С. The experimental samples obtained using the 1070°C/40 min and 1100°C/ 80 min regimes demonstrate high unbrazing temperatures equal to 1303°C and > 1330°C, respectively, which corresponds to the calculations with an accuracy of 2.5%. Taking into account the combination of properties (strength and unbrazing temperature), brazing regimes of heating to 1070-1100°C and an exposure time for 15-40 min can be recommended for the production of high-strength joints with high unbrazing temperatures.

“…Compared with the boron alloys it should be considered that the ribbon received from the alloy Ni-3.5Fe-7.5Cr-4.5Si-2.6B is amorphous [4,5] due to the presence of silicon and boron, in contrast to ribbon produced from alloys system Ni-Si-Be with the same cooling rate. Therefore the microhardness for 1301A alloy does not effect on the flexibility of the final ribbon, but for alloys with beryllium effect: there are limiting the amount of silicon and beryllium in the NiSi-Be, which you can get flexible processing ribbon.…”

Section: Measurement Of Microhardness Nickel-based Alloys With Varioumentioning

confidence: 99%

Development of rapidly quenched nickel-based non-boron filler metals for brazing corrosion resistant steels

IOP Conf. Ser.: Mater. Sci. Eng.

Kalin

Сучков

et al. 2016

Abstract. Corrosion-resistant steels are stably applied in modern rocket and nuclear technology. Creating of permanent joints of these steels is a difficult task that can be solved by means of welding or brazing. Recently, the use rapidly quenched boron-containing filler metals is perspective. However, the use of such alloys leads to the formation of brittle borides in brazing zone, which degrades the corrosion resistance and mechanical properties of the compounds. Therefore, the development of non-boron alloys for brazing stainless steels is important task. The study of binary systems Ni-Be and Ni-Si revealed the perspective of replacing boron in Ni-based filler metals by beryllium, so there was the objective of studying of phase equilibrium in the system Ni-Be-Si. The alloys of the Ni-Si-Be with different contents of Si and Be are considered in this paper. The presence of two low-melting components is revealed during of their studying by methods of metallography analysis and DTA. Microhardness is measured and X-ray diffraction analysis is conducted for a number of alloys of Ni-Si-Be. The compositions are developed on the basis of these data. Rapidly quenched brazing alloys can be prepared from these compositions, and they are suitable for high temperature brazing of steels. IntroductionNowadays the structure having lower performance because of the presence of heterogeneities, which can lead to the degradation and destruction of the joint structures during operation, is forming in the brazed joints while using filler metals containing boron [1]. Therefore, an important task is to develop non-boron filler metal.Currently the system Ni-Si-Be is poorly studied. The action of beryllium in nickel alloys in many ways similar to the action of boron; but in contrast to boron, it is highly soluble in nickel, forming an eutectic with the beryllium content of 23.8 at.%, melting at 1150 °C and consisting of a solid solution Ni (α) and low ductile intermetallic BeNi (β) [2]. The intermediate phases, worsening properties of the compound will not form in iron during brazing because of high solubility of Be, as is the case with boron. Therefore, nickel alloy containing Be, are promising for brazing steels on a par with containing boron alloys. Studies of various alloys containing beryllium, showed that they have a high specific strength and corrosion resistance [3].Analyzing all the advantages and disadvantages of the impact of beryllium on the properties of the brazed joint, can be concluded that the study of nickel alloys containing this element is extremely important field and can solve a number of problems that arise when working with boron filler metals,