Characterization and adhesion measurement of ceramic-coated nickel and titanium alloys.

摘要

Chemically inert ceramic coatings are currently being investigated to extend the lifetime of metallic components operating in severe environments. As part of this effort, the characterization and adhesion measurement of zirconium nitride and silicon carbide coatings deposited on two nickel and one titanium alloys were conducted.; Polycrystalline ZrN and amorphous {dollar}rm Sisb{lcub}0.57{rcub}Csb{lcub}0.43{rcub}{dollar} coatings were deposited by cathodic arc evaporation and by PACVD, respectively, on Incoloy 825 (Inc.), Hastelloy C22 (Hast.) and Titanium Grade 12 (Ti.) metal substrates. Analysis of the ZrN coatings by scanning electron microscopy and Auger electron spectroscopy (AES) revealed the presence of 1-8 {dollar}mu{dollar}m diameter macroparticles composed of zirconium metal. Residual stress analyses were performed on the ZrN coatings via XRD using the sin{dollar}sp2 Psi{dollar}, method. Compressive stresses of 4.06 GPa, 3.88 GPa and 2.69 GPa were found in the ZrN coatings deposited on Inc., Hast. and Ti. substrates, respectively. Residual stresses in the {dollar}rm Sisb{lcub}0.57{rcub}Csb{lcub}0.43{rcub}{dollar} coatings were estimated from reports in the literature. Nanoindentation testing was employed to assess the Young's modulus and hardness of the coatings. The Young's modulus and hardness for the ZrN coatings were 458 GPa and 27.65 GPa, respectively, while the corresponding values for the {dollar}rm Sisb{lcub}0.57{rcub}Csb{lcub}0.43{rcub}{dollar} coatings were 212.15 GPa and 21.97 GPa. X-ray photoelectron spectroscopy was employed to measure the coating composition. The ZrN coatings were composed of 58.41% Zr and 41.59% N, measured in atomic concentration. The composition of the {dollar}rm Sisb{lcub}0.57{rcub}Csb{lcub}0.43{rcub}{dollar} coatings was 57.29 at.% Si and 42.18 at.% C.; Studies of the interfacial chemistry via Auger electron spectroscopy and transmission electron microscopy revealed chemically abrupt interfaces. In addition, there was good compositional uniformity throughout the thickness of both the ZrN and {dollar}rm Sisb{lcub}0.57{rcub}Csb{lcub}0.43{rcub}{dollar} coatings.; Scratch tests were employed to assess the critical load for interfacial failure and fracture mechanisms for the various coating systems. Critical loads, characterized by continuous delamination of the coating, occurred at 41.2, 44.1 and 29.4 N for ZrN deposited on Hast. C22, Inc. 825 and Ti. 12, respectively. Interfacial failure of the {dollar}rm Sisb{lcub}0.57{rcub}Csb{lcub}0.43{rcub}{dollar}-coated metallic substrates was dominated by brittle fracture of the {dollar}rm Sisb{lcub}0.57{rcub}Csb{lcub}0.43{rcub}{dollar} coating. Critical loads of 2.9, 3.9 and 6.8 N were obtained for {dollar}rm Sisb{lcub}0.57{rcub}Csb{lcub}0.43{rcub}{dollar} deposited on Inc. 825, Hast. C22 and Ti. 12, respectively. Work of adhesion values were calculated from two well known models, namely, the Bull-Rickerby and Laugier, and from a model which incorporates elastic-plastic indentation. The ranking of the adhesion for the coating-metal substrate combinations is (from best to worst): ZrN/Inc. 825, ZrN/Hast. C22, ZrN/Ti, {dollar}rm Sisb{lcub}0.57{rcub}Csb{lcub}0.43{rcub}{dollar}/Ti, {dollar}rm Sisb{lcub}0.57{rcub}Csb{lcub}0.43{rcub}{dollar}/Hast. C22 and {dollar}rm Sisb{lcub}0.57{rcub}Csb{lcub}0.43{rcub}{dollar}/Inc. 825.; The plate impact spallation technique was also employed to investigate the interfacial spallation strength of ZrN and {dollar}rm Sisb{lcub}0.57{rcub}Csb{lcub}0.43{rcub}{dollar} ceramic coatings to nickel- and titanium-based alloys. Time restrictions with the equipment permitted testing of only a few samples. Therefore, the data obtained was qualitative in nature. In most cases, spallation occurred in the metal substrates and not at the interface as intended. However, in all cases where metal spallation occurred, the ZrN coatings remained adherent to the metal. For the {dollar}rm Sisb{lcub}