2.3. Wear Testing

The friction and wear test was done to evaluate wear rate, the coefficient of friction and wear mechanism of the EP, BFRP and GFRP composites. There were a total of four types of friction and wear test involved that was divided into two stages of tests. The first stage involved dry unidirectional sliding, two-body abrasion, and slurry pot erosion test to investigate wear properties of composites under different wear condition sliding at similar load, speed and distance. The second stage involved dry adhesive sliding under unidirectional and reciprocating motion to investigate wear and friction properties of composites at different type of motions, parameters, and configurations.

The dry unidirectional adhesive wear test was performed using TR-20LE model pin-on-disc tribometer (Ducom Instruments, Bohemia, NY, USA) in accordance to ASTM G99-95a standard. The disc shape sample with diameter of 76 mm and thickness of 4 mm was used. While the 10 mm diameter of pin used was GCr15 stainless steel pin with a hardness of HRC 62. In first stage, the test parameters were set at 30 N load, 300 rpm speed and 10 km distance, while in second stage, the test parameters were set at 0.23 MPa·m/s and 0.93 MPa·m/s pressure-velocity (PV) factor and 2 km distance. Before testing, the GCr15 stainless pin was polished with abrasive papers to a surface roughness of about 0.1 μm. The weight of the sample before and after the test was taken by using high precision balance with accuracy of ±0.01 mg. Wear volume (ΔV) and Specific wear rate (Ks) was calculated using Equations (1) and (2) respectively, as stated in ASTM G99-95a standard. The operating parameters are summarized in Table 3.

where Δm is the mass loss (g) of specimens, ρ is the density of sample (g/mm³), L is the distance travel (m), and F_N is the normal load (N).

Summary of operating parameters for friction and wear tests.

Two-body abrasion wear test was performed using TR-600 model Abrasion Resistance Tester (Ducom Instruments, Bohemia, NY, USA). The sample was cut into a disc shape of 125 mm diameter and 4 mm thickness. The disc was in contact with two vitrified bonded silicon carbide abrasive wheels, grade 46 (medium coarse). The operating parameters were set at 30 N load, 300 rpm speed and 10 km distance. The weight of the sample before and after the test was taken by using high precision balance with accuracy of ±0.01 mg. Wear volume (ΔV) and Specific wear rate (Ks) was calculated by using Equations (1) and (2), respectively. The operating parameters are summarized in Table 3.

The Slurry erosion test was done by using TR-40 model Slurry Erosion Test Rig (Ducom Instruments, USA). The rectangular sample with dimension of 75 mm × 25 mm with a thickness of 4 mm was used. A mixture of medium course (size ranged from 0.2 mm to 0.63 mm) sand and water was used as a slurry item. The surface of specimens was in contact with sand particles that caused erosion on the surface of specimens. The parameters were set at 300 rpm speed and 10 km distance. The weight of the sample before and after the test was taken by using high precision balance with accuracy of ±0.01 mg. Wear volume (ΔV) and Specific erosion rate (Ks) was calculated using Equations (1) and (3), respectively. The operating parameters are summarized in Table 3.

where Δm is the mass loss of sample (g), m is mass of erodent (g) used, and ρ is the density of sample (g/mm³).

The dry reciprocating adhesive wear test was performed using TR-281M8 model. High-frequency reciprocating rig (Ducom Instruments, Bohemia, NY, USA) in accordance with ASTM G133-95 standard. The tribometer operates in a linear repeated back and forth movements creating reciprocating motion. The sample was cut into square shape with a dimension of 15 mm × 15 mm and thickness of 4 mm. The two types of counterface used, which are ball (diameter 6 mm, HRC 60) and cylinder (diameter 6 mm, thickness 9.2 mm, HRC 60) stainless steel, creating ball-on-flat (B-O-F) configuration and cylinder-on-flat (C-O-F) configuration respectively. The operating parameters were set at 70 N load, 500 rpm speed and 120 m distance. Specific wear rate (Ks) of the sample was calculated using Equation (2). The weight of the sample before and after the test was taken using high precision balance with accuracy of ±0.01 mg. The operating parameters are summarized in Table 3.