Influence of size of reinforcing phase on wear of composite material FeAl-Al2O3
Aleksy Patejuk, Bazyli Krupicz, Jan Piwnik Politechnika Białostocka, Wydział Mechaniczny, ul. Wiejska 45C, 15-950 Białystok
Annals 4 No. 11, 2004 pages 260-264
DOI:
keywords:
abstract Samples of composite material were made using the blend of technically pure iron and aluminium powders. The reinforcement consisted of previously selected three kinds of powder particles, which differed in size of the particles: below 10 μm (called f0), 20÷30 μm (called f2) and 50÷60 μm (called f5). Two-stage process of composite production was applied. First stage was conducted in static conditions 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 presenting was this same and amounted to 1 hour for all variants of sample production. The second stage of the sintering, called „principal”, was conducted in 1250°C temperature in argon protective atmosphere during 1 hour. Produced samples had forms of cylinders of 10 mm diameters and 10÷12 mm high. Erosion tests were conducted on the stand showed in Figure 2. Air pressure and angle of particle impact on the sample were the variable parameters of the experiment. Erosion tests lasted 10 minutes. The air pressure amounted to 0.3 MPa. Under this pressure the stream velocity amounted to 150 m/s. The stream impact angle equaled 90°. Quartz sand of 0.2÷0.3 diameter constituted the abrasive material. Loss measurement was conducted in one-minute time intervals up till 4 minutes and later every 2 minutes. In the consecutive stage of studies, prepared samples underwent tests of resistance to wear using following methods: „pin on disc” and stream-abrasive method. 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 ±2oC. During the whole cycle of tests, value of linear wear was constantly recorded as well as mass of the sample was periodically weighted with 0.001 g precision. Conducted tests also show that increase in share of reinforcing phase (up till 20%) in the mentioned composite, which was made in static conditions, substantially improves its resistance to erosion. Additionally, increased resistance to erosion was recorded during testing of composite materials, containing Al2O3 particles with nickel layer. It is important to mention that during conducted tests it was characteristic that the level of wear intensity of tested tribologic pairs (which roughness parameters before the sample and counter-sample testing ranged Ra = 0.1÷0.2 μm) became stable after approximately 15 minutes of testing (Fig. 3a). Resistance to erosion wear was assessed for the same samples, on which abrasive wear tests were made. Conducted tests of erosion resistance disclosed, that application of reinforcement of Al2O3 particles decreases unit wear of tested material. It was identified that the size of reinforcement particles used during the test (f0, f2 and f5) did not significantly influence the magnitude of unit wear of composite material tested particles. However, substantial influence of surface conditions of applied reinforcement phase particles on the level of composite wear was recorded (Fig. 4). When reinforcement phase particles has nickel layer on the surface, the level of unit wear decreased. Increase in quantity of reinforcement phase results in decrease in composite’s resistance to erosion. Conducted microscope observations indicate that obtained results of tested material’s erosion are probably related with increased probability of chipping of hard and brittle reinforcement phase (relating to the material containing 10% of the reinforcement). Effects of chipping watched under microscope had forms of deep holes, in which fragments of not totally removed Al2O3 particles were still present. Key words: composite material, intermetallic phase-FeAl, reinforcement-Al2O3 particles, abrasive wear, erosion wear