High-Speed Rubbing Behavior of Abrasive Coating Coated on Titanium Alloy Blade Tips

In aero-engines, abrasive coatings are typically utilized to protect the blade tip from excessive wear caused by the harder abradable sealing coating and thereby improve the sealing performance of engines. Therefore, a Ni/cBN abrasive coating was prepared on titanium alloy using electrodeposition. The high-speed rubbing tests with a linear velocity of 350 m/s and different incursion rates were performed to investigate the effect of the Ni/cBN abrasive coating on the wear behavior against NiCrAl/diatomite seal coating. Results showed that melting wear and adhesive transfer occurred on the bare blades, causing the bare blade to suffer excessive wear. While the Ni/cBN abrasive coating exhibited superior wear resistance and cutting performance. The cBN grits pullout, the abrasion of Ni matrix and transfer of seal coating to the cBN grits were the main wear mechanism of the Ni/cBN abrasive coating. Additionally, it was found that the relationship between the incursion rate and high-speed rubbing behavior is quite different for the bare blade and Ni/cBN coating. The reason for the difference in wear behavior of bare blade and Ni/cBN coating at different incursion rates was discussed in detail.

Oxidation,Mechanical and Tribological Behaviors of the Ni/cBN Abrasive Coating-Coated Titanium Alloys

In order to improve the oxidation and wear resistance of blades tip of titanium alloys as well as the sealing performance of the gas turbine engine,a Ni/cBN abrasive coating was prepared on titanium alloys through composite electroplating.Oxidation,mechanical and tribological properties of the abrasive coating were investigated.Furthermore,the effect of the oxidation on the mechanical and tribological properties was also evaluated.Oxidation results revealed that the abrasive coating underwent slight oxidation within 700℃.Meanwhile,some intermetallic compounds,Ni3Ti,NiTi and NiTi2,were formed at the coating/substrate interface during oxidation.Due to the pinning effect of cBN particles and the different thermal expansion coefficients of the coating and substrate,the coating/substrate interface was cracked after oxidation at 700℃.Tensile results showed that the presence of coating reduced the strength of the alloy significantly at room temperature,while only marginal variations of the strength of the coated and uncoated specimens at elevated temperatures.Besides,the wear tests indicated that the coating had the excellent cutting ability and wear resistance,which can effectively protect the blades tip of titanium alloys.As the temperature increased,the wear resistance decreased due to the decrease in the mechanical properties of the Ni/cBN coating.

Microstructural evolution and mechanical properties of NiCrAlYSi+NiAl/cBN abrasive coating coated superalloy during cyclic oxidation

Cyclic oxidation behavior of Ni Cr Al YSi+Ni Al/c BN abrasive coating at 900°C and the mechanical properties of the coating-substrate system were investigated.Results indicated that elemental interdiffusion occurred between the coating and substrate,which caused the formation of interdiffusion zone(IDZ)and secondary reaction zone(SRZ)during aluminization,while their compositions and structures changed with oxidation.Al N interfacial layer formed at c BN/metallic matrix interface during aluminization,while it transformed into multilayer oxides during oxidation.Due to the microstructural evolution of these interfaces,the fracture behavior and bending toughness of the system changed greatly during three-point bending tests.Besides,the damage mechanisms were discussed.