July_August_AMP_Digital

A D V A N C E D M A T E R I A L S & P R O C E S S E S | J U L Y / A U G U S T 2 0 1 9 5 2 iTSSe TSS iTSSe TSS JTST HIGHLIGHTS CONTROL OF THE MESOSTRUCTURE OF SUSPENSION PLASMA-SPRAYED COATING WITH LASER SURFACE TEXTURING: APPLICATION TO TBC R. Kromer, P. Sokołowski, R.T. Candidato, S. Costil, and L. Pawłowski Thermal barrier coatings manufactured either by at- mospheric plasma spraying or electron beam physical vapor deposition are widely used in the hot-temperature sections of gas turbines to provide thermal insulation and corrosion pro- tection. Recently, the suspension plasma spraying process has emerged for the manufacturing of thermal barrier coatings. Specific microstructures including columns can be deposited. A narrowwindowof optimal parameters remains an outstand- ing problem to produce the suitable microstructure. Lately, studies demonstrate that the substrate topography plays a significant role in the columnar structure formation. This study shows that the substrate topography obtained via laser surface texturing enables a regular columnar structure. The laser beam generates peaks and cavities regularly arranged on the surface. The plasma spray parameters were selected to produce columnar structures linked to the substrate topogra- phy. The suspension composition and coating microstructure were studied. Superalloy samples with bond coats were used as substrates. The results show that the columnar coating microstructure canbeadjustedbyoptimizing the laser process parameters. The improved coating structure features more than 500 columns per mm 2 . Substrate surface topography op- timization and suspension plasma spraying can improve the performance of thermal barrier coating systems (Fig. 1). POWDER DEVELOPMENT AND QUALIFICATION FOR HIGH-PERFORMANCE COLD SPRAY COPPER COATINGS ON STEEL SUBSTRATES Dominique Poirier, Jean-Gabriel Legoux, Phuong Vo, Bruno Blais, Jason D. Giallonardo, and Peter G. Keech This paper presents the development work undertaken to tailor Cu powder size specifications to produce dense cold spray Cu coatings featuring strong adherence on steel sub- strates. Through review of historical data generated in the course of developing Cu coatings for corrosion protection of used (nuclear) fuel containers, it was found that particle size distribution isparticularlycritical tomeet applicationadhesion requirementsof 60MPaandprevent nozzlecloggingduringap- plication; D01 and D90 were fixed at 5 and 60 µm, respectively. The effect of powder size on coating microstructure and ad- hesion was further investigated with four Cu powder lots pre- senting different granulometries. The four lots were analyzed for composition, hardness, microstructure, and morphology. T he Journal of Thermal Spray Technology (JTST), the official journal of the ASM Thermal Spray Society, publishes contributions on all aspects—fundamental and practical—of thermal spray science, including processes, feedstock manufacture, test- ing, and characterization. As the primary vehicle for ther- mal spray information transfer, its mission is to synergize the rapidly advancing thermal spray industry and related industries by presenting research and de- velopment efforts leading to advancements in implementable engineering applications of the technology. Articles from the February and April issues, as selected by JTST Editor-in-Chief Armelle Vardelle, are highlighted here. In addition to the print publication, JTST is available online through springerlink.com. For more information, visit asminternational.org/tss. Fig. 1 — Three-step quantitative analysis of ceramic topcoats: (a) surface image capture; (b) counting of columns; and (c) measuring column widths. 12