Microstructure and lifetime of Hf or Zr doped sputtered NiAlCr bond coat/7YSZ EB-PVD TBC systems

Abstract

The microstructural and chemical evolution after different processing steps of Ta-containing NiCoCrAlY bond coats (BC) sprayed by high velocity oxy-fuel on Ni-base superalloy (SA) substrates, top-coated with 7YSZ and furnace cycled at 1100 ºC focusing along the BC/SA interfaces is presented. Three superalloys were selected considering their Ta content relative to that within the BC: a) no Ta in the superalloy composition (IN100) and either b) similar or c) higher Ta content with respect to the BC (M247LC SX and CMSX-4, respectively). The processing conditions were as-sprayed, as-annealed, after EB-PVD deposition of a 7YSZ top coat, and after furnace cyclic tests (1100 ºC /120 h). The evolution of chemical composition after the different process steps are presented that include a normalization criteria to a Ni-Al-Cr system, elemental profiles as well as Weibull distribution plots of minor containing elements such as Ti, Ta, Mo, or W at the BC/SA interface. The effect of Ta was activated in some coated substrates by the presence of Ti and C in the superalloy consisting of inward Ta-diffusion, trapping of outward diffusing Ti and the subsequent formation of (Ta, Ti)-rich carbides in the BC avoiding possible segregation effects as titanium oxide in the oxide scale.

The mechanisms of controlling FCT life and failure mode of Ni-based EBPVD YSZ thermal barrier coatings via the effects of both substrate elements and reactive element doping

“…The FCT results of the Zr-doped samples of [52] in Fig. 6 apparently confirm the statement previously made for Y-doped samples in this study: the service life of TBCs becomes shorter, as the content of refractory elements in the substrates IN100 and CMSX-4 increases as to 1.3 → 5.5 at%.…”

“…In this chapter, PVD related FCT experiments on TBC systems having a magnetron-sputtered bond coat doped with either Zr or Hf have been carried out by Saldaña, Schulz, Mondragón Rodríguez, Caceres-Diaz, and Lau. They are referred to in [52]. The magnetron-sputtered bond coats are Ni-36 Al-11Cr-0.8 X in at% with X being Zr or Hf.…”

Microstructural analysis of Ta-containing NiCoCrAlY bond coats deposited by HVOF on different Ni-based superalloys

“…Plotting the composition data measured by EDS in a Ni-Al-Cr ternary system following the site preference criteria of transition metals, reported by Jiang [29,36] allowed to predict the diffusion paths and thus the correspondent phase contents from the different processing conditions ( Figures 7 and 8). Based on the mentioned site preference criteria the following normalization model at 1100 °C was used for BC and superalloys: (Ni + Co + 0.28Mo + Re) (Al + Ti + 0.72Mo + Hf + W + Ta) (Cr) [36]. For instance, in the as-sprayed systems, Figure 7a shows the composition from the as-sprayed coatings in a 1100 ºC isothermal section of the Ni-Al-Cr ternary phase diagram, whereas the as-annealed system from coated IN100 superalloy is represented in Figure 7b.…”

Effects of Al Sputtering Film on the Oxidation Behavior of NiCrAlY Bondcoat

“…The state of art topcoat material is 6-8 wt.% yttria-stabilized zirconia (YSZ) ceramic coating, which provides the advantages of low thermal conductivity, high thermal-expansion coefficient, and high fracture toughness [9][10][11]. YSZ topcoat can be deposited by mainly two methods: electron beam physical vapor deposition (EB-PVD) and air plasma spray method (APS) [12][13][14]. Interlayer bondcoat is between bond topcoat and substrate, which protects the superalloy substrate from being oxidized in severe environments and serves the critical role of providing adhesion between the substrate and the topcoat [15,16].…”