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Microstructural, electrical, thermal and tribological studies of copper-fly ash composites through powder metallurgy

Thanga_Kasi_Rajan S., Balaji A. N., Narayanasamy P., Vettivel S. C.

Bulletin of the Polish Academy of Sciences. Technical Sciences

2018

Vol. 66, nr 6

935--940

This research work address the fabrication of copper (Cu) matrix composites, reinforced with fly ash (FA) particulates with 3, 6, 9 and 12 wt.% using the powder metallurgy route. The microstructural, physical, electrical, thermal, mechanical and tribological properties of thus fabricated Cu-FA composites have been studied. Optical microstructural characterization of the composites exposed persuasively uniform distribution of FA reinforcement with minimum porosity. The mixed powder SEM images revealed the homogeneous dispersion of fly ash particulates in the copper matrix. The hardness values showed improvement with increase in the weight percentage of FA in the Cu matrix. Electrical conductivity was measured using the four-point probe method at room temperature. Thermal conductivity was measured with a thermal diffusivity analyzer at room temperature. The fly ash addition leads to weakening the conductivity of Cu-FA composites. The tribological properties of Cu-FA composite specimens were investigated using a Pin-on-disc tribo testing machine against an EN81 steel contour disc. The specific wear rate of the composites tended first to decrease, which was attributed mainly to the formation of a mechanically mixed layer on the worn surface. Then it would increase as the FA content increased because of reduction in ductility and brittle oxide cracks associated with adding more FA particulates. It seems that composites with FA percentages below 9wt.% have optimum properties of microstructure, hardness and wear resistance, which is suitable for applications such as electrical sliding contacts, electrical discharge machining and spot welding electrodes.

Tribological Properties of Copper-Based Composites with Lubricating Phase Particles

Juszczyk B., Kulasa J., Malara S., Czepelak M., Malec W., Cwolek B., Wierzbicki Ł.

Archives of Metallurgy and Materials

2014

Vol. 59, iss. 2

615--620

The results of research into influence of chemical composition on structure and tribological properties of copper-based composites intended for slide bearings are presented in this paper. The study was focused on copper alloys with lubricating phase particles in form of graphite, tungsten disulphide (WS2), molybdenum disulphide (MoS2) and glassy carbon. The metallic matrix of composite materials was composed of alloys from Cu-Sn-Zn system. The mass content of lubricating phase particles was from 5 to 20%. The process of production of subject materials included the processes conducted with full or partial contribution of liquid phase and it was conducted by two methods. Both the method of classic powder metallurgy and stir casting method were used for the production of composites. Lubricating phase particles heated to the temperature of 200°C were introduced to liquid metal bath and then the process of stirring and casting to moulds was performed. In case of production of composites by powder metallurgy, the process included mixing of bronze powders and lubricating phase particles, and then their consolidation. Sintering process was conducted in temperature between 750-800°C. The produced materials were tested in terms of microstructure and tribological properties with the CSM Instruments tribometer.

W pracy zamieszczono wyniki badań dotyczące wpływu składu chemicznego na strukturę oraz właściwości tribologiczne materiałów kompozytowych na osnowie miedzi przeznaczonych na łożyska ślizgowe. Przedmiot badań stanowiły stopy miedzi z udziałem cząstek faz smarnych w postaci grafitu, dwusiarczku wolframu (WS2)), dwusiarczku molibdenu (M0S2) oraz węgla szklistego. Metaliczną osnowę materiałów kompozytowych stanowiły stopy z układu Cu-Sn-Zn. Udział masowy cząstek faz smarnych wynosił od 5 do 20%. Proces wytwarzania badanych materiałów obejmował procesy przebiegające z całkowitym oraz częściowym udziałem fazy ciekłej i przebiegał dwutorowo. Do wytwarzania kompozytów zastosowano zarówno metodę klasycznej metalurgii proszków, jak i metodę topienia i odlewania z jednoczesnym mieszaniem tzw. stir casting. Do ciekłej kąpieli metalicznej wprowadzono podgrzane do temperatury 200°C cząstki faz smarnych a następnie realizowano proces mieszania i odlewania do form. W przypadku otrzymywania kompozytów na drodze metalurgii proszków proces obejmował mieszanie proszków brązu oraz cząstek faz smarnych, a następnie ich konsolidację. Proces spiekania prowadzono w temperaturze z zakresu 750+800°C. Wytworzone stopy poddano badaniom mikrostruktury oraz oceny właściwości tribologicznych na tribometrze CSM Instruments.

Structure of metal matrix composites with an addition of tuff

Łach M.

Archives of Foundry Engineering

2010

Vol. 10, iss. 3 spec.

135--140

The article presents preliminary results of tests of metal matrix composites structure which was modified by an addition of powdered volcanic tuff. Distribution and shape of ceramic particles as well as the quality of the bonding along the tuff- metal matrix interface were studied. Depth of tuff element diffusion in the matrix as well as diffusion in tuff particles were checked. Micro-hardness and porosity of the composites were also tested. The tuff from Filipowice near the town of Krzeszowice was used for the tests. Powder metallurgy was applied to obtain the composites and the matrix materials were copper and 316L steel powders. The tuff was introduced in 2, 5 and 10 % by weight. To remove water from the channels of aluminosilicates, the tuff was baked at 850oC for 4 hours and then cooled together with the oven. The tests revealed good quality of the bonding of the tuff particles and the matrix and their even distribution. The addition of tuff improved the hardness of the composites and reduced their porosity which has great significance because of possible applications of this kind of materials in general and copper composites in particular. This gives grounds for further studies on volcanic tuff use in metal composites.