Friction and wear characteristics of natural bovine bone lubricated with water

• Research on the friction and wear behaviour of natural bovine bone was conducted.
• The key technology on servo valve was materials selection of spool and sleeve.
• The bovine bone has good tribological property because of its special structure.
• The wear mechanism of CFRPEEK and natural bovine bone are adhesive wear.
• The bovine bone/Al2O3 ceramics pair has excellent friction and wear properties.

Natural bovine bone has the potential to act as a bearing surface for spool-in-sleeve servo valve of water hydraulics. To screen material combinations for that application, friction and wear tests were conducted on the following three pairs: 316 L stainless steel on natural bovine femoral cortical bone (NBFCB), carbon fibre reinforced polyetheretherketone (CFRPEEK) on NBFCB, and Al2O3 ceramic on BFCB. Tests were conducted on a face-loaded, annular ring-on-ring configuration with water lubrication. The worn surfaces were studied using an environmental scanning electron microscope (ESEM). The effects of normal pressure and sliding velocity on the friction and wear characteristics are discussed. Friction coefficients decreased with increasing velocity and pressure, and a running-in process was observed. The weight loss due to wear of the NBFCB was larger than that of the counterpart materials. Sharp reductions in both friction coefficient and wear rate were observed for NBFCB when sliding against Al2O3 compared to sliding against 316 L and CFRPEEK. The 316 L steel wore by micro-cutting, and the wear mechanism of the Al2O3 ceramic was fatigue wear. The wear mechanism of CFRPEEK was mainly adhesive wear. The wear mechanism of NBFCB was brittle fracturing when sliding with 316 L and the Al2O3 ceramic, and it was adhesive wear when sliding against CFRPEEK.