Abstract
Turbine blades in aviation engines and land based gas-turbines are exposed to extreme environments. They suffer damage accumulation associated with creep, oxidation and fatigue loading. Therefore, advanced repair methods are of special interest for the gas-turbine industry. In this study, CMSX-4 powder is sprayed by Vacuum Plasma Spray (VPS) on single-crystalline substrates with similar compositions. The influence of the substrate temperature is investigated altering the temperature of the heating stage between 850 °C to 1000 °C. Different spray parameters were explored to identify their influence on the microstructure. Hot isostatic pressing (HIP) featuring fast quenching rates was used to minimize porosity and to allow for well-defined heat-treatments of the coatings. The microstructure was analysed by orientation imaging scanning electron microscopy (SEM), using electron backscatter diffraction (EBSD). The effects of different processing parameters were analysed regarding their influence on porosity and grain size. The results show that optimized HIP heat-treatments can lead to dense coatings with optimum γ/γ′ microstructure. The interface between the coating and the substrate is oxide free and shows good mechanical integrity. The formation of fine crystalline regions as a result of fast cooling was observed at the single-crystal surface, which resulted in grain growth during heat-treatment in orientations determined by the crystallography of the substrate.
Highlights
Kalfhaus et al / Materials and Design 168 (2019) 107656 fatigue caused by static and alternating mechanical and thermal stresses drive elementary damage processes which govern the exploitable life of high temperature components
All scanning electron microscopy (SEM) micrographs taken from interface regions in the as-sprayed conditions for all type A samples (Table 3) look similar
A very fine dispersion of complex shaped γ′ particles can be recognized, which forms as a result of the slow cooling of the sample after powder deposition in the vacuum plasma spraying (VPS) chamber
Summary
T. Kalfhaus et al / Materials and Design 168 (2019) 107656 fatigue caused by static and alternating mechanical and thermal stresses drive elementary damage processes which govern the exploitable life of high temperature components. The most critical high temperature components in gas turbines are turbine blades, which are often made of single-crystalline nickel-based superalloys [1,2]. High costs associated with a replacement of single-crystal turbine blades make repair procedures attractive. When new material is added by coating procedures, it is important that the added material is well bonded and has similar mechanical features as the substrate. The repaired parts should show similar material properties and performance parameters as the original turbine blades prior to service exposure
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
