Brazing Of Ceramics Research Articles

Application of Gyrotron Radiation for Coating and Welding

ABSTRACTThe availability of high power high frequency microwave sources of up to tens of kW has opened up important technological and industrial applications of microwave radiation. The particular use of gyrotrons for generating the high power microwaves is considered.The application of high power microwaves for fusing wear resistant coatings onto refractory materials is discussed, together with the brazing of ceramics, welding together of thick metal parts and the rapid heating and curing of polymers for high reliability long life environmental coatings.It is shown that the use of high power gyrotron radiation enables considerable improvements to be made on conventional technologies for high temperature processing of materials and enables the development of new and efficient processes.

Metal/ceramic joining.

This review article on metal/ceramic joining is subdivided into the description of research activities in the fields of active metal brazing and diffusion bonding published in the last decade. Informations are given on active metal brazing of oxide, nitride, and carbide ceramics and on diffusion bonding of alumina, zirconia, magnesia, silicon nitride, aluminum nitride and silicon carbide ceramics to metals. Ultra high vacuum diffusion bonding and experiments using the model combination Nb/alumina are also regarded. Emphasis is laid on a concise reproduction of experimental data concerning the bonding conditions and the determintion of bond strength. The review demonstrates that much effort was devoted to studies on the formatin of interfacial reaction layers and on the efficiency of interlayers additonally introduced between the ceramic and the metal part to reduce internal stresses caused by thermal expansion misfit of the materials to be bonded.

クロムメタライズ法によるＳｉＣセラミックスと金属との銀ろう付 Ｉ

A new chromium (Cr) metallization process was developed for brazing or soldering of SiC ceramic to metal. This report describes the characteristics of Cr metallization, bond strength and helium leak rate of the silver brazed layer.SiC ceramics used in the experiments was hotpress-sintered material containing a small amount of BeO. It has a high thermal conductivity (270 W/m.K) and also a high electrical resistivity (1014Ω.m). Silver brazing of SiC ceramics to metal was carried out at 1073K using eutectic alloy of 72wt% Ag-28 wt% Cu.The results of this study are as follows, (1) Cr metallization was achieved by printing Cr paste on the surface of SiC ceramics, and then heating the ceramics at a temperature between 1173K and 1273K for 1.8ks in Ar atmosphere.(2) The thickness of Cr metallized layer did not depend on the thickness of printed Cr paste under the same heating condition.(3) The bending strength of the SiC/SiC and SiC/WC-Co hard alloy, brazed layer were 320MPa and 360MPa respectively at 723K and fractured through SiC. The fracture remained in the brazed layer at temperatures above 773K.(4) The helium leak rate of the silver brazed layer (combination: SiC/A1203, SiC/kovar, SiC/WC-Co) was less than 1.2×10-10 atm.cc/s even after the thermal cycle testing.

Brazing of SiC Ceramics with Active Metal

Brazing of SiC Ceramics with Active Metal

Thermal stability of composite materials based on some boride-oxide systems

1. The basic laws controlling reactions in the TiB2-MgO, TiB2-CaO, TiB2-Al2O3, and TiB2-Y2O3 systems have been established by thermodynamic analysis and experiment. 2. Temperature limits have been determined for the use of composite materials based on borideoxide systems as active solid ceramic brazing materials suitable for joining refractory metals to high-temperature electrically insulating ceramics.