ICMCTF2016 Session TS2-2: Thermal Spray Technologies and Coatings

A new processing method called Plasma Spray-Physical Vapor Deposition (PS-PVD) has been developed to fill the gap between conventional thermal spray processes and vapor phase methods. This technology allows for the deposition of advanced materials as either thin, dense coatings or vapor-deposited columnar microstructures by changing the processing conditions. PS-PVD operates in the range of 1-5 mbar and can deposit coatings from 10-500 microns thick with high throughput over large areas. Coating material can be vaporized and incorporated into the gas stream, allowing for some non line-of-sight deposition. The materials flexibility and microstructural variability make this technique attractive for a wide range of applications including solid oxide fuel cells and gas sensors, but the main focus will be on materials for turbine engine hot section components. Materials processing-property relationships for thermal and environmental barrier coatings deposited using the PS-PVD facility at NASA Glenn Research Center will be discussed in the context of microstructure, phase and crystallinity, thermal conductivity, erosion, and mechanical properties. In addition, the deposition of composite coatings and metastable oxide states will also be explored with potential applications.

Bulk metallic glasses (BMGs), also called amorphous alloys, have totally different structure from the conventional crystalline metals and are well-known for their high strength and high hardness, large elastic limits, and, in particular, for their outstanding corrosion and wear resistance. During the past several decades, despite the understanding on the formation and microstructure, as well as the mechanisms related to their unique mechanical properties have achieved great progress, industrial applications of BMGs are still very scant due to mostly the poor ductility at room temperature. In contrast, amorphous coatings based on BMG systems have received increasing attention and interest in recent years because of the combination of the excellent properties inherited from the bulk glassy alloys and the potential engineering applications for amorphous coatings. In this talk, we will report the the recent progress of amorphous coatings made in the author’s group, including fabrication, microstructure, and properties of Fe-based amorphous coatings, and the enhancement of bonding strength and impact tolerance of the coatings by structure modifications. In addition, we will also briefly talk about the foreseen potential applications of this new type of advanced materials.

WC-10Co-4Cr chrome replacement coatings were deposited by two different HVOF coating techniques namely JP 5000 and JetKote. In this study, effect of process conditions and feedstock materials on coating micro-structure and composition was studied. Plasma diagnostics was employed in order to assess the particle state during coating process and its effect upon subsequent coating characteristics. Coatings were also characterized using X-ray diffraction, SEM-EDS analysis and ASTM B 117 corrosion testing.

In this work sliding wear resistance of WCCoCr thermal sprayed coatings obtain from different grain size was examined. The layers applied on flat samples using two types of powders: conventional grain size of 25 µm and an ultra-fine, nanostructured grain size <10 microns. As counter samples were used ball made from different materials: hard solid ceramics (SiC) and carbon-graphite impregnated with resin. The condition of the surface of the specimens and counter specimens was determined before and after tribological tests (3D laser profilometry, SEM, EDS). Tested coatings from ultrafine power proved to have higher wear resistance than the coating from conventional powder.