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 8 4 8 iTSSe TSS iTSSe TSS T he Journal of Thermal Spray Technology (JTST), the official journal of the ASM Thermal Spray Society, publishes contributions on all aspects—fundamental and prac- tical—of thermal spray science, including processes, feedstock manufacture, testing, and char- acterization. As the primary ve- hicle for thermal spray information tranfer, its mission is to synergize the rapidly advancing thermal spray in- dustry and related industries by presenting research and development efforts leading to advancements in imple- mentable engineering applications of the technology. Ar- ticles from the April and June issues, as selected by JTST Editor-in-Chief Armelle Vardelle, are highlighted here. In addition to the print publication, JTST is available on- line through springerlink.com . For more information, visit asminternational.org/tss. JTST HIGHLIGHTS FABRICATION AND CHARACTERIZATION OF PLASMA-SPRAYED CARBON-FIBER- REINFORCED ALUMINUM COMPOSITES Jiang-tao Xiong, Hao Zhang, Yu Peng, Jing-long Li, and Fu-sheng Zhang Carbon fiber (C f )/Al specimens were fabricated by plas- ma-spraying aluminumpowder on unidirectional carbon fiber bundles (CFBs) layer by layer, followed by a densification heat treatment process. The microstructure and chemical com- position of the C f /Al composites were examined by scanning electron microscopy and energy-dispersive spectrometry. The CFBs were completely enveloped by an aluminummatrix and the peripheral regions of the CFBs were wetted by aluminum. In the wetted region, no significant Al 4 C 3 reaction layer was found at the interface between the carbon fibers and alumi- nummatrix. Mechanical properties of theC f /Al specimenswere evaluated. When the carbon fiber volume fraction (CFVF) was 9.2%, the ultimate tensile strength (UTS) of the C f /Al compos- ites reached 138.3 MPa with elongation of 4.7%, 2.2 times the UTS of the Al matrix (i.e., 63 MPa). This strength ratio (between the UTS of C f /Al and the Al matrix) is higher than for most C f /Al composites fabricated by the commonly used method of liq- uid-based processing at the same CFVF level (Fig. 1). PRACTICAL ASPECTS OF SUSPENSION PLASMA SPRAY FOR THERMAL BARRIER COATINGS ON POTENTIAL GAS TURBINE COMPONENTS X. Ma and P. Ruggiero Suspension plasma spray (SPS) has attracted extensive efforts and interest for producing finely structured and func- tional coatings. In particular, thermal barrier coatings (TBCs) applied by SPS have gained increasing interest due to the potential for superior thermal protection of gas turbine hot sections as compared to conventional TBCs. Unique colum- nar architectures and nano- and submicrometric grains in the SPS-TBC demonstrate some advantages of thermal shock durability, low thermal conductivity, erosion resistance, and strain-tolerant microstructure. This work aimed to look into some practical aspects of SPS processing for TBC applications before it becomes a reliable industry method. The spray capa- bility and applicability of the SPS process to achieve uniform thickness and microstructure on curved substrates were em- phasized in carefully designed spray trials to simulate coating fabrication on industrial turbine parts with complex configura- tions. The SPS-TBCs were tested in erosion, falling ballistic im- pact, and indentational loading tests to evaluate performance in simulated turbine service conditions. Finally, a turbineblade was coated and sectioned to verify SPS sprayability inmultiple critical sections. The SPS trials and test results demonstrate that SPS is promising for innovative TBCs. However, some Fig. 1 — Microstructure of C f /Al composites strengthened by carbon fiber bundles of 750 filaments. Fig. 2 — Plot of TBCmicrohardness HV300 via spray distance used in the SPS spray trials. 14