J. Karwan-Baczewska

Copper Metal Matrix Composites Reinforced by Titanium Nitride Particles

Copper based Metal Matrix Composites are promising materials for electrical and electrotechnical applications such as electronic packaging and contacts, resistance welding electrodes, heat exchangers etc. Introducing the ceramics particles into the copper matrix allows to achieve a higher mechanical properties comparing to pure copper. The literature shows the variety of reinforcement materials are used. The most commonly strengthening phase include: oxides Al2O3,Y2O3, SiO2, carbides SiC, WC, TiC, ZrC, borides TiB2, ZrB2 and others such us volcanic tuff, carbon or intermetalic phases Al-Fe. [1-7]. It is obvious that reinforcement material without TiN leads to decrease the electrical conductivity of copper. Preliminary investigations concerning nanoscale Cu-based composites with TiN particles were presented in papers [10, 11]. Powder metallurgy (PM) process leads to obtain uniform distribution of strengthening phase in matrix. In order to achieve uniform distribution the process parameters such as mixing and selection the sizes of particles must be appropriate selected. The another factor of decreasing the mechanical and electrical properties by using PM route is porosity. Conventional PM process includes pressing and sintering does not always allow to achieve the high density what is one of the main criterion for high electrical conductivity material. The hard ceramic particles in metal matrix which are not deformable make difficult the densification process. In some cases the use of more advanced methods of production is desirable. The use of titanium nitride particles is justified by their high electrical conductivity in compare to the other reinforcement materials.

Influence of Molybdenum and Boron Addition on Fracture of P/M Parts

Samples made of iron powder with addition of 1.5 and 2% of molybdenum and 0-0.6% of boron were compacted at 600 MPa and sintered at 1200°C for 60 minutes in hydrogen atmosphere after mixing in Turbula mixer. The samples were deformed in a tensile test till rupture. The effect of molybdenum and boron on topography of fracture is discussed. It is noted that the sintering mechanism changes upon addition of boron particles into Fe-Mo alloy. The fractures of the studied samples were observed by means of scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The addition of Mo influences the change of fracture to ductile type. The type of fracture is brittle with Mo and borides segregating to grain boundaries. In the alloys with low concentrations of molybdenum boron induces brittle transgranular fracture.

Microstructure and Tribological Properties of Aluminum Matrix Composite

AlSi5Cu2 alloy matrix composite have been studied by microscopic examination and basic tribological properties was evaluated. Composite material was produced by the mechanical milling and spark plasma sintering technique. After sintering process SiC particles were uniformly distributed in the matrix. The wear and the friction coefficients were determinate as a function of the SiC volume fraction. The addition of SiC wt. % had significant effect on tribological properties of that composites. The increase in reinforcement content improves the wear resistance of obtained materials.

Structural Investigations of Iron-Based Sintered Alloys after Plasma Nitriding

Various nitriding methods are applicable, viz.: gas nitriding, nitriding in powders and plasma nitriding which is one the latest nitriding technologies applicable for parts made of constructional and tool steels. A large of motor car products made from iron-based alloying powders has been subjected to plasma nitriding process in order to enhance their surface properties like: hardness and abrasive wear. One of the main problems of chemical heat treatment alloys produced by powder metallurgy technology is their porosity degree. In the experiments Fe-Ni-Cu-Mo and Fe-Mo sintered structural parts modified by boron were made. Boron activates the sintering process which results in their considerable consolidation in the sintering at 1473 K for 60 minutes in the atmosphere of hydrogen. The experiments are related to the production of sintered structural elements based on iron powder - NC 100.24 as well as Astaloy Mo (Fe-Mo) and Distaloy SA (Fe-Ni-Cu-Mo) modified by 0.2 wt%, 0.4 wt% and 0.6 wt% B. Sintered parts were obtained by mixing powders said above, followed by compacting at 600 MPa pressure and sintered at 1473 K during 60 minutes time in hydrogen atmosphere. Selected sintered parts were plasma nitrided at 883 K during 4 hours time. After plasma nitriding microstructure morphology using light microscopy and phase identification by Xray diffraction technique have been made. The influence of structure and phase composition on the surface properties of examined sintered parts modified by boron, after plasma nitriding have been analyzed.