| The existing of large residual stress in coatings may cause plastic deformation or fracture. The residual stress controlled will greatly improve the performance of coatings. In this paper, Ti/Ti N/Zr/Zr N multilayers were deposited on Si wafer and TC11 alloy substrate by arc ion plating technology respectively. We have studied the phase structure, thickness, adhesion and hardness of the multilayer coatings by means of XRD, SEM, scratch tester, micro-hardness tester respectively. We have used the substrate curvature method to study the effect of modulation period, modulation ratio and coating thickness on the residual stress of multilayer coatings. The effects of static mechanics properties and high-cycles fatigue behaviors of Ti/Ti N/Zr/Zr N multilayer coatings on TC11 titanium alloy substrate were studied by tensile test and rotary bending fatigue test.Ti/Ti N/Zr/Zr N multilayer coatings were deposited on Si wafer and TC11 titanium alloy substrate with the modulation period of 1551 nm, 856 nm, 488 nm and 267 nm, respectively. Residual compressive stress of multilayer coatings on Si substrate is 1.252 GPa, 0.781 GPa, 0.565 GPa and 0.493 GPa, respectively. While the residual compressive stress on TC11 titanium alloy substrate is 3.526 GPa, 3.215 GPa, 3.153 GPa and 3.081 GPa, respectively. The residual compressive stress of multilayer coatings decreases with the decrease of modulation period. The microhardness increases from 2061.10 HV to 2547.98 HV, and the adhesion increases from 49 N to 58 N.We have prepared the Ti/Ti N/Zr/Zr N multilayer coatings with modulation ratio(LTi/Ti N:LZr/Zr N) of 1.68:1, 1.29:1, 1:1.37 and 1:1.94 respectively. Residual compressive stress of multilayer coatings deposited on Si substrate is 0.381 GPa, 0.430 GPa, 0.558 GPa and 1.079 GPa, respectively. The residual compressive stress of multilayer coatings decreases with the decrease of modulation ratios. The microhardness of multilayer coatings increases from 2349.74 HV to 2876.16 HV, while the adhesion decreases from 60 N to 50 N.The Ti/Ti N/Zr/Zr N multilayer coatings with different thickness were deposited on Si and TC11 titanium alloy substrate respectively. The residual compressive stress on Si substrate is 0.629 GPa, 0.810 GPa and 1.216 GPa for the 4.5μm, 7.4μm and 9μm coating thickness, respectively. While the value on TC11 titanium alloy substrate is much larger, which is 2.991 GPa, 3.091 GPa and 3.136 GPa respectively. By changing the thickness from 4.5μm to 9μm, the residual compressive stress on both substrates increases, the microhardness increases from 2746.96 HV to 3090.92 HV, and adhesion increases from 62 N to 71 N.Ti/Ti N/Zr/Zr N multilayer coatings with a modulation period of 276 nm and modulation ratio of 1.5:1 were deposited on TC11 titanium alloy substrate. We have investigated the fatigue life, fatigue strength and fatigue fracture of coated and uncoated samples. The results showed that under low stress, the multilayer coatings can improve the fatigue properties of the titanium alloy substrate, while the result is contrary for the coated samples under high stress. The increase values of fatigue life decreases from +40.82% to-36.88% with the stress between 520 MPa and 650 MPa. The fatigue limit of coated sample is 474 MPa which is 6% larger than that of uncoated sample. |
PDF Full Text Request