1. Also from each melt, one plate, measuring 1.5 x 6 x 12 in. were cast. From this plate, 6 blocks were cut from which 6 fatigue specimens were machined, thus 12 fatigue specimens were tested from each composition. Samples taken from the gating system of the web casting were used for friction test- ing. A number of specimens were prepared from each com- position for these tests. Figures 2 and 3 show the machined dimensions of the tensile test bars and fatigue specimens, respectively. The samples for friction testing were machined to 18 x 12 x 8 mm.
Tribological Properties
A Falex block-on-ring friction and wear testing machine (Figs. 4 and 5) was used to carry out the tribological tests in accordance with the ASTM standard procedures D2714. At first, a couple of dry tests at different loads and speeds were performed on the Alloy 3, however a loud noise was gener- ated after a couple of hundreds of test cycles. Most of those tests had to be stopped well before achieving the number of cycles required by the standard (5,400 cycles) due to a sud- den increase in the coupon temperature (>150°C) and a very unpleasant high-pitched noise.
Lubricated wear tests were then performed on the three ma- terials, and only those will be discussed in this paper. The tests were run at room temperature using VG10 grade oil which has a room temperature viscosity close to that of typi- cal turbine oil (VG32 grade) at a temperature of 50°C. The contact load between the coupon and the ring was set to 100 lb with a ring speed of 780 rpm resulting in total test dura- tion of 7 min. The load was applied to the block right after the desired speed was reached. Three tests were conducted for each material.
Fatigue Limit
The ISO Standard 7905-2 was followed to conduct the fatigue tests. The test method requires loading the specimen up to 50 million stress cycles with a frequency ranging from 50 Hz to 80 Hz. All the tests were performed at the Royal Military College, Kingston, Ontario.
Results and Discussion Composition
The chemical composition from each experiment is given in Table 1. The target composition was met with considerable ac- curacy. There were slight differences between the bismuth and tin contents in the two melts that made up one alloy composi- tion, but these differences were minor and should have no effect on test results. Of the twenty tensile bars for each composition, four were tested at room temperature and four at each of the elevated test temperatures, (100, 150, 200 and 250ºC).
Mechanical Properties
The average mechanical properties are shown in Table 2 and plotted in Figs. 6 and 7. Figure 6 shows the data separated by composition, and Fig. 7 shows the data separated by specific property. The data show that the bismuth-containing alloys have promising mechanical properties compared with the lead- ed alloy. Alloy 1, containing 5% bismuth, had better properties than Alloy 2 which contains 10% bismuth. Alloys 1 and 3 had comparable yield strength and elongation at all test tempera- tures; as the test temperature reached its maximum, Alloy 3 had the best mechanical properties followed by Alloy 1. The prop- erties of Alloy 2 fell below the typical properties of the leaded alloy C93700. With the exception of yield strength, Alloys 1 and 3 had good properties up to 150ºC, as observed previously for other leaded and Bi-containing alloys.3
At higher test tem-
peratures, the properties of all the alloys fell below the typical room-temperature properties of typical C93700 alloy.
rich in copper and tin has a very high hardness ranging between 200 and 400 HV
while lead measures 10 HV . The matrix hardness of Alloy
1 is higher than that of Alloy 2 due to its copper content. The matrix softens a considerable amount in Alloy 3 after testing at 250ºC, while the hardness of the matrix in Al- loy 1 is stable after the high temperature test. Since there
Vickers microhardness testing was completed using a 10 g force with 15 s dwell time; the results are shown in Ta- ble 3. Bismuth is harder than lead – bismuth averages 30 HV
. The alpha-delta eutectoid
Table 2. Average Mechanical Properties from Alloys Tested
22
International Journal of Metalcasting/Winter 10
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