A comparison of techniques for the metallographic preparation of thermal sprayed samples

Conference · Tue Jan 01 00:00:00 EST 1991

OSTI ID:5563620

Smith, M F; McGuffin, D T; Henfling, J A ^[1]; Lenling, W J ^[2]

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1. Sandia National Labs., Albuquerque, NM (USA)
2. Thermal Spray Technologies, Watertown, WI (USA)

Metallographic preparation of thermal spray coated samples is often difficult because hard and soft materials, which normally require different polishing techniques, are commonly present in a single spray-coated sample. In addition, the microstructures of many spray-deposited materials make them prone to pull-out damage during cutting, grinding, and polishing operations. We have compared alternative metallographic techniques to prepare three common types of thermal sprayed coatings: (1) a plasma sprayed alumina-titania wear coating, (2) a plasma sprayed zirconia thermal barrier coating, and (3) on HVOF (High Velocity Oxy-Fuel) sprayed tungsten carbide/cobalt (WC/Co) hardcoating. Each coating was deposited onto a steel substrate and was prepared with metallographic protocols based on: (a) silicon carbide (SiC) papers, (b) bonded diamond platens, and (c) diamond slurries. Polishing with SiC papers generally produced edge rounding and significant pull-out that increased the apparent porosity of the coatings. Polishing with bonded diamond platens produced better results, but some pull-out was still observed. In addition, this method is typically the most expensive due to the limited lifetime and high cost of the platens. Preparation by diamond slurry lapping produced the best overall results at a reasonable cost per sample. Porosity artifacts produced by polishing with SiC papers and bonded diamonds platens also resulted in spuriously low hardness values for the WC/Co samples, but hardness results for the two ceramic coatings were not affected by the polishing method. 4 figs., 2 tabs.

• Research Organization: Sandia National Labs., Albuquerque, NM (United States)
• Sponsoring Organization: USDOE; USDOE, Washington, DC (United States)
• DOE Contract Number: AC04-76DP00789
• OSTI ID: 5563620
• Report Number(s): SAND-90-3032C; CONF-9105107-1; ON: DE91014704
• Resource Relation: Conference: 4. national thermal spray conference and exposition, Pittsburgh, PA (United States), 5-10 May 1991
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM OXIDES
MICROSTRUCTURE
PROTECTIVE COATINGS
POLISHING
TITANIUM OXIDES
TUNGSTEN CARBIDES
COBALT
SPRAY COATING
STEELS
SUBSTRATES
WEAR
ALLOYS
ALUMINIUM COMPOUNDS
CARBIDES
CARBON COMPOUNDS
CHALCOGENIDES
COATINGS
CRYSTAL STRUCTURE
DEPOSITION
ELEMENTS
IRON ALLOYS
IRON BASE ALLOYS
METALS
OXIDES
OXYGEN COMPOUNDS
REFRACTORY METAL COMPOUNDS
SURFACE COATING
SURFACE FINISHING
TITANIUM COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
TUNGSTEN COMPOUNDS
360201* - Ceramics
Cermets
& Refractories- Preparation & Fabrication
360202 - Ceramics
Cermets
& Refractories- Structure & Phase Studies