The specific wear rates of the coatings against both counterbody materials are displayed in Fig.1. The NiSF_HF coating wore at a rate of 5.00×107mm3/Nm against the WC-Co counterbody and 1.10×106mm3/Nm vs. the Al2Og counterbody. Meanwhile the NiSF_LF coating wore at a rate of 5.43× 107 mm3/Nm against the WC-Co counterbody and 1.23×10-6 mm3/Nm vs. the Al203 counterbody. Both coatings were seen to wear significantly more when tested against the Al2O3 counterbody in comparison to WC-Co, with the specific wear rate increasing by 120% and 127% for the NiSF_HF andNiSF_LF coatings vs. Al2O3 in comparison to WC-Co. The specific wear rates of the counterbodies were also measured; in all tests the WC-Co counterbodies were found to undergo negligible wear, with no flat surface forming on the contact surface of the ball with this material. In contrast the Al2O3 counterbodies were seen to visibly wear during the test with a flat surface forming on the ball. The mean specific wear rates of the Al2O3 balls tested vs. the NiSF HF and NiSF_LF coatings were measured as (4.85±0.95)×107mm3/Nm and (1.36±0.42)×107mm3/Nm respectively.
Fig.1.Specific wear rates of the coatings and counterbodies.
The coefficient of friction measured in each wear tests vs. distance travelled by the counterbody against both materials are displayed in Fig.2. Against both counterbody materials, the break-in period occurs for approximately the first 100 m travelled with large variations incoefficient of friction u measured; however, while u is seen to remain relatively constant at a value of about 0.6 for the remaining distance when tested against Al2O3, it can be seen to decrease during the test in the wear tests vs. WC-Co for both coatings from a maximum of about 0.7 down to below 0.5. The change in u throughout each test was found to be similar for the NiSF_HF and NiSF_LF coatings, suggesting little to no difference in the wear mechanisms taking place in the wear of eachcoating. The final value of the coefficient of friction was seen to be greater for both samples tested against the Al2O3 counterbody compared to WC-Co.
Fig.2.Coefficient of friction vs.distance travelled for the wear tests against the WC-Co and Al2O3 counterbodies.
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