PSI - Issue 60

Nagaraja Bhat Y V et al. / Procedia Structural Integrity 60 (2024) 345–354 347 Y V N Bhat, M A Davinci, A Kumar, N L Parthasarathi, S I S Raj, D Samataray, B.K. Sreedhar / StructuralIntegrity Procedia 00 (2019) 000– 000

Chemical composition of SS440C used for the present work is given in the Table 1. This composition is as per ASTM A 276. The material was received in billet form and discs of 120 mm diameter & 10 mm thickness and hemispherical pins of 8 mm diameter & 20 mm length were machined out of it. The hemispherical end of the pin ensures a Hertzian contact (i.e., sphere on a flat surface) between the pin and the disc at the beginning of experiments. The image of the disc and pins used for the experiments are shown in Figure 1. Heat treatment of pin and disc was carried out as per the following procedure. Preheating was done in steps by first heating the material to 650 o C, holding it at this temperature for 30 minutes and then further heating it to 850 o C for 30 minutes. Then, austenitization was carried out at 1065 o C for 15 minutes followed by high speed quenching upto 49 to 55 o C. Further, cryogenic cooling was done at -49 o C followed by double tempering at 250 o C for 2 hours. After the heat treatment, the hardness of the steel was measured as 56  1 HRC.

Fig. 1. SS440C Pin and Disc used for the experiments

Fig. 2. Tribo-Meter

2.2. Experiments

Figure 2 shows an image of the Pin-on-Disc Tribo-Meter (Model TR-20LH-M1Ducom make) used for the experimental studies. Tribological experiments at ambient temperature were carried out as per procedure given in ASTM G99. The frictional force between the disc and pin is measured by a load cell, while the wear depth is measured by an LVDT installed in the Tribo-Meter.

Table 2. Experimental parameters used for the study

Case

Load (N)

Velocity (mm/s)

Sliding Distance (m)

Remarks

Case – 1

10

5

800

Intermittent operation

Case – 2

10

15

800

Intermittent operation

Case – 3

10

15

800

Continuous operation

Case – 4

10

30

800

Continuous operation

Case – 5

20

30

800

Continuous operation

The parameters used for the experiment are given in Table 2, which are selected based on the requirements of the fuel handling machine of PFBR. Each experiment was repeated thrice to ensure repeatability. Experiments for Cases-1 and 2 were done intermittently by performing the tests for every 100 m of sliding distance and then stopping for examination. This intermittent testing was done till the completion of 800 m of sliding distance. Experiments under Cases-3 to 5 were performed at one stretch for 800 m sliding distance.