Comparative Study on the Thermal Performance of Cr-CrxOy and YSZ-CoNiCrAlY Coatings Exposed at 900 °C

Yttria stabilized zirconia (YSZ) thermal barrier coatings (TBCs) deposited on CoNiCrAlY oxidation protective bond coats are commonly required in temperature regimes up to 1200 °C (e.g., hot gas turbine regions) due to their superior thermal behavior and mechanical properties. For temperatures up to around 900 °C, oxidation protection can be alternatively provided by metallic-ceramic Cr-CrxOy coatings. For the present research, Cr-CrxOy atmospheric plasma sprayed (APS) and YSZ-CoNiCrAlY APS-high velocity oxy-fuel TBC coatings were deposited on a NiCr20Co18Ti substrate. The samples were isothermally heat treated at 900 °C for 10 h in an environmental atmosphere and subsequently isothermally oxidized at the same temperature for 1200 h. Investigations of the physical, chemical, and mechanical properties were performed on the as-sprayed, heat-treated, and oxidized samples. The oxidation behavior, microhardness, cohesion, and adhesion of the samples were correlated with the microstructural investigations and compared to the conventional TBC system. It could be shown that heat treating decreased the Cr-CrxOy coatings crack susceptibility and led to the formation of a protective thermally grown Cr oxide layer. The experimental work on the YSZ-CoNiCrAlY system revealed that the phase composition of the bond coat has a direct influence on the oxidation protection of the coating system.

Effect of Low Temperature Heat Treatment for R512E Coated C-103 Nb Alloy

The article aims to investigate the feasibility of oxidation protection imparted to C-103 Nb-based alloy by fused slurry silicide coating of R512E (60Si20Fe20Cr) carried out at lower temperature (1200 °C) for higher dwell time i.e. 12 hours. The findings reveal that the coating treated can impart sufficient oxidation resistance the alloy, which may withstand the desired application conditions wherein oxidation protection for smaller time period is needed. Moreover, this treatment is not found to deteriorate other mechanical properties of the alloy in 'As coated' condition.

Facile fabrication and low-temperature bonding of Cu@Sn–Bi core–shell particles for conductive pastes

Cu@Sn–Bi core–shell particles were synthesized and used as conductive fillers of ink applied to flexible printed circuits. This work provides new insights into the low-temperature bonding and anti-oxidation protection of Cu-based conductive pastes.

Polymer Derived Ceramics from Si, B, SiB6, and Mo5SiB2 Filler-Loaded Perhydropolysilazane Precursors as Protective and Functional Coatings for Refractory Metal Alloys

Oxidation barrier coatings on the base of a perhydropolysilazane precursor with different amounts of Si, B, SiB6 and Mo5SiB2 (T2) fillers for the oxidation protection of Mo-Si-B alloys were developed. The influence of different filler compositions as well as the influence of pyrolysis conditions (temperature and atmosphere) was studied. The coating slurries were examined with respect to their rheological behavior, which allows optimization of the coating slurry. Dilatometry studies show that the coefficient of thermal expansion of the composites can be matched to refractory, especially molybdenum alloy based, substrates by varying the content and the composition of the filler. The pyrolyzed coating systems offer a low porosity, which is one of the key parameters to a high oxidation protection capability.