Péter Baumli

Interaction between a titanium-containing molten salt and an alumina plate

In the present paper the chemical interaction between an alumina plate and a one-phase NaCl-KCl-K2TiF6 as well as two-phase NaCl-KCl-K2TiF6/Ti system has been studied experimentally at 700 oC during 2 hours, as function of K2TiF6 content of the melt. In all experiments the reaction product TiO2 of an exchange reaction has been found at the surface of the alumina plate. Its thickness changes through a maximum point as function of the K2TiF6-content of the melt, as a result of the competition of two processes: the exchange reaction leading to the formation of the TiO2 layer, and its dissolution in the melt.

Wettability of Carbon Surfaces by Molten Alkali Chloride Mixtures

The wettability of graphite and glassy carbon surfaces by molten alkali chlorides was measured by the sessile drop method. Pure NaCl, KCl and CsCl, binary NaCl-CsCl and NaCl-KCl and ternary NaCl-KCl-CsCl compositions were measured. CsCl was found to be an interfacially active component (at the solid/liquid interface) in both binary NaCl-CsCl and ternary NaCl-KCl- CsCl systems. From the composition dependence of the interfacial energy in the NaCl-CsCl system the hypothesis is made on the possibility of the existence of 3[ 4 ] Cs NaCl complex.

Influence of KOH on the carbon nanostructure of peanut shell

Carbon nanostructured materials, including nanosheets, are being produced from a variety of natural waste materials. The process involves activation and carbonization. Potassium hydroxide (KOH) is ...

Grain boundary behavior of copper with C45 medium carbon steel

Brazing is one of the most important techniques known in joining two similar/dissimilar metals/metal–nonmetal combinations for structural, mechanical, and aerospace applications. Brazing joints are...

Coating of 1.4404 stainless steel by a combination of brazing and nitriding

In the current research, surface hardening of 1.4404 stainless steel was investigated. A hard Ni-containing coating was prepared by brazing at 1150 °C using a Ni foil with Si powder. The hardness behavior was increased by nitriding as well. The nitriding experiments were performed at low and high temperatures (460 and 640 °C) for a different period (3 and 6 h). The microstructure and material properties were characterized using scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and Micro Vickers hardness testing. Results show that the hard phase and the binding Ni foil were well distributed into the hard layer. The hard coating material was composed of a Si-phases and Ni-containing compound dispersion. After the nitriding, the hardness of the samples was increased with increasing the nitriding time and temperature and increasing the brazing time. The 10 min brazing and 6h nitriding at 640°C resulted in 32% higher hardness than the non-nitride sample. Strong metallurgical bonding is formed between the stainless steel substrate and the coating layer, as well as between the binding Ni foil and the hard phase; because of the mutual diffusion of alloying elements, the hardness of this hard coating was 2 to 3 times higher than the initial hardness of steel substrate.

Development of nitrided selective wave soldering tool with enhanced lifetime for the automotive industry

The aim of our research is to develop an economic material combination exhibiting good wetting with solder alloy melts and enhanced lifetime against erosion in lead-free soldering applications. Iron-nitrides have strong bonds compared to metals, therefore they are expected to have increased resistance against erosion in solder melts compared to iron soldering tools. The first step of our research is to find the proper substrate material for nitride coating to obtain the desired wetting behaviour. The present paper focuses on the substrate material selection through wetting examinations of nitrided W302, 42CrMo4 and C45 steels with SAC 305 solder alloy melt. It was found that the substrate composition strongly affects the wetting contact angle. The best wetting was achieved with the C45 type steel substrate. The correlation between substrate composition, compounds formed during nitriding and wetting behaviour is discussed.