Change of wear of the composites on aluminium matrix cooperating with a cast iron ring and a cast iron and ceramic ring
Marek Grabowski, Jerzy Cybo, Andrzej Posmyk Uniwersytet Śląski, Zakład Badań Warstwy Wierzchniej, ul. Śnieżna 2, 41-200 Sosnowiec
Annals 1 No. 1, 2001 pages 19-22
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abstract The paper presents a change of tribological properties of rolled composites AlMg4+Al2O3 of the following reinforcement phase content: 0.4, 3.9, 4.3 volumetric %, co-acting with a cast iron and ceramic ring and a cast iron ring. The results of tribological examination of the pairing: composite/cast iron (Fig. 5, 6) show that even a small fraction of the reinforcing phase has a significant influence on mass decrements of both cooperating elements. The mass decrement of pure alloy AlMg4 (without Al2O3 addition) during the cooperation with a cast iron roll is larger when compared to the mass loss of the cast iron. This is caused by greater hardness of cast iron. An introduction of hard ceramic particles of Al2O3 transfers the coope-ration onto the contact surface of ceramic particles and cast iron. This causes that with the increasing content of Al2O3 in the alloy AlMg4, mass loss of the cast iron ring increase, whereas they simultaneously decrease for a composite material. Already at the lowest phase content (variant A) the decrement of cast iron mass increases almost five times and that of the composite material decreases by about 70%. For composites of the largest reinforcement phase content this wear is lower by about 85%, whereas the wear of the cast iron ring grows 9 times (Fig. 5). The largest wear rate was noted in the initial period of the association’s cooperation, lasting about 5 hours. This overlaps the period of the initial grinding-in phase (about 7 hours) recorded in the diagram of the friction coefficient changes (Fig. 6). After complete grinding-in of the pairing (about 12 hours), stabilization of the friction coefficient takes place, which fluctuates within the limits μ = 0.07÷0.08. Different are the changes of the friction coefficient and mass decrement during the cooperation of the pairing: composite/cast iron and ceramic material. The influence of the reinforcement phase on the wear of the pairing’s elements is insignificant and does not exceed 0.0007 g (Fig. 3) for both materials, which in comparison to the pair composite/cast iron is a slight value. Such low wear can be explained by great hardness of both co-acting materials. The reinforcement phase content is of greater importance for the changes of the friction coefficient. With an increase of Al2O3 particles content in a composite the friction coefficient value goes down (Fig. 4). It reaches 0.015 for the lowest Al2O3 content (variant A) and about μ = 0.008 for a composite of the highest Al2O3 content (variants B and C). An evident difference of the character of co-acting and wear of both compared associations is documented in Figure 2. Summing up, it must be said that the application of two composite materials reinforced with Al2O3 phase in a tribological association ensures the improvement of friction and wear characteristics by an order of magnitude in relation to the pair: composite/cast iron. A ten times smaller friction coefficient and mass decrements show the possibility of using such materials for working elements of piston machines.