Diffusion of sputtered inconel 617 coatings in titanium

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INCONEL 617 coatings 10-to 13-μm thick were radio frequency (RF) magnetron sputtered onto commercially pureα-titanium substrates and heat-treated at 800 °C for 2 hours. The resulting structures were examined in cross section by scanning electron microscopy (SEM) and analytical transmission electron microscopy (TEM). Scanning electron microscopy of polished and etched cross sections showed that the coating remained continuous, and as a result of inter-diffusion, a layer 66-μn thick had formed below the coating. Examination of the coating near the free surface by TEM showed it contained both M23C6 and M6C carbide precipitates, while several micron-thick layers containing intermetallic phases such as σ, γ′, and Ti2Ni were found near the substrate. Kirkendall voids 75 to 300 Å in diameter were present near the original INCONEL 617/α-titanium interface. The microstructure further below that interface contained a thin layer of titanium martensite and Widmanstätten α + Ti2Ni. No TiNi or TiNi3 was found. The diffusivity of nickel and titanium was reduced several orders of magnitude and is attributed primarily to the formation of intermetallic compounds in the coating and substrate. © 1990 The Metallurgical of Society of AIME.

Publication Title

Metallurgical Transactions A