Influence of conditions of cyclically variable loading on tribology properties of composite material FeAl-Al2O3
Aleksy Patejuk*, Tomasz Durejko** *Politechnika Białostocka, Wydział Mechaniczny, ul. Wiejska 45C, 15-950 Białystok **Wojskowa Akademia Techniczna, Instytut Automatyzacji Systemów Dowodzenia i Logistyki, ul. Kaliskiego 2, 00-908 Warszawa
Annals 4 No. 11, 2004 pages 265-268
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abstract Samples of composite material were made using the blend of technically pure iron and aluminium powders. 3-4 samples were made for each technological variant. In the process of sintering, a mix of Fe and Al powders in proportions of 60 and 40% atm. was used. The reinforcement of the composite material was made of (Al2O3) in the amounts suitably 10 and 20% of the total weight in two types: I - (Al2O3) grains had crude surface, II - grains (Al2O3) had an additional nickel coating 2÷3 μm thick. The technological process of making such materials consisted of two phases: pre-sintering and principal sintering. The first phase was conducted in a hydraulic pulsar under the load of 300 MPa and in the conditions of cyclically variable loading of 40 Hz frequency. Temperature of the process in both cases was this same and amounted to 660°C. The time of pre-sintering was the same and amounted to 1 hour for all variants of sample production. The second stage of sintering, called „principal”, was conducted in 1250°C temperature in argon protective atmosphere. Prepaired samples (minimum 3 ones of each type) underwent tests of resistance to wear using following methods: „pin on disc”. In abrasive tests, load of 3 MPa and linear velocity of 0.5 m.p.s. were used. Steel 45 thermally resistant to 45 HRC hardness was the counter-sample. The test lasted 2 hours. Temperature in direct proximity of cooperating steam amounted to 25±2°C. During the whole cycle of tests, value of linear wear was constantly recorded as well as mass of the sample was periodically weighted. The result of the test presented on the graph shows that the amount of reinforcement phase consisted particles Al2O3 substantially adds to the material wear resistance. Previous researches proved that the more reinforcement coating is used (up to 20% of total weight) in the composite sample, made in a static environment, the more durable material is created. However, this tendency is not applicable to the sample materials made in cyclically variable loading environment. In a such case, the tendency was exactly opposite to the previous one and it was verified on a double amount of samples made in this technological variant. A positive influence of nickel coating applied on reinforcement phase was also notified. The best parameters achieved the composite materials consisted 10% of Al2O particles with a nickel coating (2÷3 μm thick) constituted on its surface. Hardness is the primary parameter contributed to abrasive wear resistance so the next stage of the experiment included hardness measuring, using Vickers' method under the load of 50 N. Results of the tests showed that participation of reinforcing phase (regardless the size of applied particles) should not be regarded as a factor, which insignificantly influences the level of hardness. There is a certain upward relation between the particle hardness and increase in reinforcement quantity. A little influence of nickel layer on hardness of particle reinforcement was noted, as well. Key words: composite material, intermetallic phase-FeAl, reinforcement-Al2O3 particles, abrasive wear