Wyniki 1-2 spośród 2 dla zapytania: authorDesc:"MAREK NYKIEL"

Badania procesów spiekania i właściwości kompozytów na osnowie miedzi zawierających tuf wulkaniczny DOI:10.15199/28.2015.4.4

  This paper describes metal matrix composites reinforced with different type of ceramic particles. The most important types of ceramics reinforced metal composites as well as new trends associated with the use of porous particles or spheres as reinforced particles were presented. A brief overview of volcanic tuff from the region of Krzeszowice and electrolytic copper powder was presented. Manufacturing method of copper matrix composites containing different volume fractions of volcanic tuff was described. Using dilatometer the thermal analysis of sintering process of copper matrix composites with varying content of tuff was conducted. Dilatometric study was performed in two sintering atmospheres: nitrogen 6.0 and hydrogen 6.0. The effect of the sintering atmosphere and an addition of tuff on the kinetics of sintering process and shrinkage (density) of obtained composites was examined. The higher content of the tuff particles, the lower shrinkage during sintering. The use of a hydrogen atmosphere during sintering results in a greater density of the sintered composites in comparison to nitrogen one. The results of properties research of sintered copper matrix composites reinforced with tuff were presented. The influence of the contents of tuff on the electrical conductivity and softening temperature are shown. The addition of tuff increases the softening temperature. It is of key importance in the case of application of such materials for electrodes to resistance welding. This paper presents examples of microstructures of sintered copper matrix composites reinforced with tuff of volcanic origin. Distribution of introduced particles is uniform. The quality of particle — matrix connection is satisfactory. The results of these studies shows that volcanic tuff can be an interesting material used as reinforcement in metal matrix composites. Key words: powder metallurgy, copper matrix composites, sintering, volcanic tuff, resistance welding electr[...]

Solidification process of sintered AISI 316L austenitic stainless steel powder modified with boron-containing master alloy

  Wrought stainless steels have wide range of applications as consequence of their corrosion resistance in aggressive environments. Powder metallurgy (P/M) technology can increase range of application of stainless steel through significant reduction of manufacturing costs by simplifying production process. Unfortunately, manufacturing by P/M process created, in structure component, undesired porosity which greatly reduces corrosive resistance of sintered steel. A reduced open porosity can be usually attained by forging or other mechanical treatment. Of course such an operations increase costs. In order to keep manufacturing costs on reasonable level, it is desired to eliminate porosity during already existing manufacturing process. One of the possibilities is proper chemical modification of base alloy to induce appearance of liquid phase during sintering in order to achieve high density sinter. Many researchers indicated boron as an excellent activator for sintering ferrous alloys. Boron added to iron creates lowmelting eutectic liquid (1177°C) which activates densification mechanisms: (i) particles rearrangement by decreasing friction forces among the particles, (ii) fragmentation of particles by liquid penetrating grain boundaries. Moreover, presence of eutectic liquid in some cases under specific conditions during sintering process may lead to appearance of non-porous superficial layer. Such a layer is characterized by the lack of solidified eutectic liquid what greatly improves corrosive resistance of sinter by eliminating electrochemical corrosion cells. The creation of nonporous superficial layer usually requires addition of the high amounts of boron (higher or equal to 0.4 wt %) which during cooling solidifies as a brittle eutectic on grain boundaries drastically lowering mechanical properties of sinter [1]. Loss occurs especially when solidified liquid creates the continuous network surrounding grains [2]. Dispersing of [...]

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