Kazimierz Friedel

Electron beam activated brazing of cubic boron nitride to tungsten carbide cutting tools

Abstract New tool materials are needed for efficient and high-grade finishing of difficult-to-work materials such as cladded and sprayed layers, cast iron and hardened steels. Advanced superhard materials based on diamond are in common use. However, cubic boron nitride (CBN), as a material for efficient tools, seems to be better than natural diamond. Obtaining reliable cubic boron nitride–tungsten carbide joints is an essential problem in the production of cutting tools with this superhard material. There are different methods of fixing CBN into a tool body. One of them, electron beam activated brazing, seems to be very promising. An electron beam, used as a heat source in this process, enables the precise control of heat delivered to the tool parts during brazing as well as high cleanliness of the joint due to lack of gas impurities in the vacuum environment. Using an experimental design method based on Taguchi techniques for quality engineering, it was found that the heating time, the electron beam current and the roughness of the CBN surface influence mostly the joint shear strength.

The influence of filler particle shapes on adhesive joints in microwave applications

Electrical conduction of adhesive joint is provided by the metal content. High conductivity requires high metallic content. Isotropic electrically conductive adhesives are usually manufactured with filler concentration sufficiently greater than percolation threshold to guarantee low resistance with allowance for manufacturing tolerances. But we have found that it is not sufficient in a case of microwave applications. In this work we have measured the quality factor of resonant circuit at the frequency of 3.5 GHz, which was made as stripline circuit including the measured joints. Adhesives were formulated on the base of two kinds of resin with four type of silver filler. Filler materials differ from each other as regards the shape of particles and their dimensions. It was stated that kind of silver filler, the interaction of filler/type of resin as well as the state of the surface of adhesive layer plays important role in the case of solder replacement with electrically conductive adhesives in microwave electronics.

The optimization of a triode electron gun with a thermionic cathode

Abstract This paper describes the systematic method of an electron gun optimization. The properties and quality of high power electron beams formed by an electron gun were evaluated by measuring the electron beam emittance as a very sensitive figure-of-merit. Our objective was to decrease the electron beam emittance by identifying the most significant factors which influence the electron beam quality and selecting the most preferable set of these factor levels. For this purpose we used the experimental design method based on Taguchi techniques for quality engineering. This technique proved to be a useful tool in identifying the significant factors, optimizing its levels and decreasing the electron beam emittance. As a result of our experiments we have obtained an optimized electron gun which produces an electron beam with an emittance by one order of magnitude lower than the emittance of a currently used beam. It was proven that the repeatability of electron beam characteristics after each cathode replacement is quite satisfactory provided that the cathode is placed in its optimum position.

A systematic method for optimizing the electron beam hardening process

The objective of this study was to identify the significant conditions to provide electron beam surface hardening of heat treatable carbon steel. Computer modelling to determine the dependence of surface hardness and hardened layer thickness on the electron beam energy density is presented. Using swept line electron beam hardening in an installation developed for carrying out experiments on surface hardening, the experimental results were in good agreement with those from calculations and confirm that it is impossible to assess the hardened layer thickness and uniformity or to find the most suitable processing conditions by measuring the mean value of surface hardness only. The detailed investigation of cross-sections is indispensable. The experimental design applied in this paper has proved to be a useful statistical tool for optimizing electron beam surface hardening.

Management of waste electrical and electronic equipment in Poland - Ecological, organizing and economical aspects

According to regulations of Directive 2002/96/EC of the European Parliament and of the Council of the 27 January 2003 on waste electrical and electronic equipment, UE Member States are obligated to ensure high level of separate collection, specified rate collection and levels of recovery including recycling of waste electrical and electronic equipment. Rational working WEEE (waste electrical and electronic) management system as well as high pro-ecological attitude of society are required to fulfill imposed obligations. Within the framework of the paper WEEE management system existing in Poland will be described. Imposed obligations, treatment processes, aims and advantages of WEEE management will also be shortly described.

Systematical error of the measurement of electron beam emittance

Abstract Determination of the structure of electron beam charge flow is one of the most important problems in designing and in investigations of the electron beam. The parameter that enables the quantitative estimation of non-laminar behaviour of electron beams is the emittance. This parameter can be measured using hole-slit analyzer. However, this type of equipment belongs to the group of measuring devices for which the results of measurements are loaded with systematical errors ΔE. For a hole-slit analyzer errors arise from finite dimensions of holes and analyzing slits. Here the original method of evaluating the systematical errors of emittance measurements is presented, allowing estimation of real emittance values E r , by the determination of correlation coefficient κ E , which is characteristic of the measuring device and from the emittance E m range, using the relation E r = κ E E m . The ability to allow for the error in emittance measurement permits estimation of various properties of different types of electron beams and to compare their charge flow laminarity. Information is given on the principle and design of an analyser with movable apertures for beam exploration with the results derived.

Application of glow discharge electron gun to surface modification

Abstract Surface modification of a material requires a known temperature field in the treated zone resulting from the technology of specific materials processing and related with the power density distribution of a surface heat source and heat conduction. Glow discharge electron gun was developed to realise the electron beam heat source of modified power density distribution. A numerical analysis of two-dimensional heat transfer for a flux of energy with optional distribution w ( r ) irradiating the material surface was carried out. The selection of a proper cathode geometry, electron beam power, working distance and interaction time makes it possible to obtain predicted temperature distribution in the treated material and expected shape of modified zone. The surface modification by an electron beam of modified power density distribution is expected to provide greater selectivity and precision of the treated area.