Completed Projects of Brazing Technology

 

Adamant - Immunize of Ni and Fe based filler metals to improve bonding properties

Short description:

The manufacture of high-strength joints using a wide variety of brazing technologies is state of the art in a wide range of industrial sectors. The classes of Ni- and Fe-based filler metal alloys have proved particularly suitable for applications at high temperatures and simultaneous corrosive stress, such as in the exhaust tract of motor vehicles or for the repair of turbine blades. The alloying concepts of the Ni and Fe filler metals most commonly used in industry are very similar and are based on the respective main alloying element, i.e. Ni or Fe, Cr to improve corrosion resistance and mechanical properties, and elements which lower the melting point. Typically, the metalloids silicon, boron and phosphorus are used for this purpose. However, these elements favour the formation of hard and brittle phosphides, borides and silicides. The brittle phases are not only metallurgical notches, the phase bands formed from them also fail brittle due to their low toughness, so that spontaneous component failure occurs in case of overload. Previous concepts for avoiding these brittle phases are associated with very high technical effort and economic costs. One possibility, which has not been considered so far, is the improvement of the mechanical properties by interrupting the hard phase bands by means of targeted precipitation formation. The addition of even small amounts of Ti can significantly improve the strength of these brazed joints. The aim of the project is to investigate this approach and make it usable for industrial application.

Funding:	Arbeitsgemeinschaft industrieller Forschungsvereinigungen „Otto von Guericke“ (AiF)
Porject number:	21.231 N
Duration:	June 1, 2020 to November 30, 2022

 

2BeSafe2 - Development of design concepts for the assessment of the fatigue strength of brazed joints under consideration of process-related brazing seam conditions

Short description:

As a result of efforts to further increase engine performance and environmental policy objectives, the demands on dynamically stressed components in the automotive sector are constantly increasing. In order to use the fuel more and more efficiently, engines with gasoline direct injection operate with ever higher injection pressures in the common rail systems of p > 350 bar with simultaneous reduction of wall thicknesses. An economical design of these highly dynamically loaded brazed joints is of great importance. The few currently available approaches for evaluating the fatigue strength of brazed joints do not take into account the real, microscopic condition of the brazed seam, but refer to idealized fillets. In addition, various damage mechanisms occur that have not been considered in the design concepts so far. This results in a relatively large dispersion, which makes it necessary to design components much more conservatively than necessary.This problem, which is particularly relevant in the automotive industry, is to be solved in this project by deriving reliable design concepts for brazed joints with realistic brazing seam conditions. Different influencing variables such as type and duration of the brazing process, but also geometrical deviations of the component geometries are recorded and used to derive holistic design concepts.

Funding:	Arbeitsgemeinschaft industrieller Forschungsvereinigungen „Otto von Guericke“ (AiF)
Porject number:	20.370 N
Duration:	January 1, 2019 to June 30, 2022

 

Influence of solid-liquid reactions in the brazing gap on joint properties and precision

Short description:

The aim of the subproject A5 is to reduce the quantity of intermetallic compounds in the brazing seam and the effect of the heat treatment on the base material when joining hot work tool steels with a nickel-based filler metal. Thus, the mechanical and thermal properties of the joint will be improved. In order to achieve this, the grain growth will be reduced by an adapted temperature control and by electric current assisted brazing which results in accelerated and directed diffusion during brazing. Poster SFB 1120 – Teilprojekt A5

Funding:	German Research Foundation (DFG)
Porject number:	SFB 1120 – Project A5
Duration:	July 1, 2018 to June 30, 2022

 

Surface pretreatment of steel sheets for die casting of gap-free and low-distortion cast aluminum/steel sheet metal hybrids

Short description:

The aim of the research project is to produce gap-free and low-distortion hybrid Al/steel-components by high pressure die casting. For this purpose, coatings are applied on steel insert by means of thermal spraying and deposition brazing, which enable a metallurgical bonding or solid form closure connection to the steel sheet and Al-cast during the casting process. Partial melting of the coating during casting facilitates the cracking of the oxide scales present on the coating surface, supporting the metallurgical bonding. The influence of the different coating deposition processes on the wetting behavior of the coatings, the formation of the intermetallic phases at the Al/steel interface as well as the melting and oxidation behavior of the coatings is investigated. Poster BO 1979/39-1

Funding:	German Research Foundation (DFG)
Porject number:	BO 1979/39-1
Duration:	January 1, 2015 to June 30, 2018

 

Prevention of binder-related defects due to reliable processing of brazing pastes in for large-area joints

Short description:

Brazing pastes consist of a filler metal and organic binders. In practice, the organic binder leads to defects such as pores, inclusions or wetting defects, especially in large-area joints. The aim of the project was to extend the usability of brazing pastes to large-area and complex component geometries and to avoid the formation of defects. In the first step, a comprehensive process understanding of defect formation in the brazing process was developed. This included a thorough investigation of binder-related residues and the investigation of the decomposition and degassing behaviour of organic binders using various thermoanalytical methods. Subsequently, it was possible to significantly reduce the formation of defects by means of various process engineering and material technology approaches. In the case of Ni-based filler metals, the controlled removal of the resulting vaporous decomposition products of the binder by structuring the brazing paste, and the addition of a carbide-forming element for binding of organic residues, have proven to be successful to achieve pore free joints. Poster 17.907 N

Funding:	Arbeitsgemeinschaft industrieller Forschungsvereinigungen „Otto von Guericke“ (AiF)
Porject number:	17.907 N
Duration:	01.11.2014 bis 31.08.2017

 

Systematic analysis of the influence of surface conditions on brazed joints with application-oriented methods III

Short description:

The aim of the research project is to increase the brazing process reliability by avoiding brazing defects induced by surface contaminations. For this purpose, the influence of different surface conditions on the joint quality was analysed systematically. Defined surface conditions were produced by a variation of machining processes, contamination by cooling lubricants and subsequent cleaning processes. The quality of the brazed joints was determined by non-destructive and destructive testing methods. Poster IGF-Nr. 18.387 N

Funding:	German Federation of Industrial Research Associations (AiF)
Porject number:	IGF-Nr. 18.387 N
Duration:	January 1, 2014 to July 31, 2017

 

Evaluation of the fatigue strength of safety-related brazed components

Short description:

The aim of the research project is to develop evaluation strategies for the fatigue strength of brazed joints in safety-related components such as rails for direct fuel injection. Additionally to the analysis of the joining process and of the influence of the macroscopic fillet, numerous characteristic geometric values of the brazed joints were determined for a detailed quality assurance. The influence of these geometric values on the fatigue strength was evaluated. Subsequently, the results were transferred to a more complex, component-like pipe joint. Poster IGF-Nr. 17.766 N

Funding:	German Federation of Industrial Research Associations (AiF)
Porject number:	IGF-Nr. 17.766 N
Duration:	August 1, 2013 to December 31, 2016