Chemical vapor deposition of erosion-resistant TiB/sub 2/ coatings

Technical Report · Sat Mar 31 23:00:00 EST 1984

OSTI ID:6923900

Caputo, A J; Lackey, W J; Wright, I G

Erosion- and wear-resistant coatings are needed for numerous applications, including valve and pump components for coal liquefaction and gasification plants. Titanium diboride is unusually hard and stable and offers considerable promise for use in highly erosive and corrosive environments. We deposited TiB/sub 2/ coatings by hydrogen reduction of TiCl/sub 4/ and BCl/sub 3/. Our objective was to correlate process variables with coating structure and properties, with emphasis on obtaining coatings having high erosion resistance. We varied deposition temperatures from 750 to 1050/sup 0/C and the TiCl/sub 4/ and BCl/sub 3/ flow rates. Commercial cemented carbides and experimental nickel-bonded TiB/sub 2/ were used as substrates. After structural characterization, the resistance of the deposited coatings to erosion was determined by a hot coal-oil slurry impingement test. The deposition rate was very temperature dependent, ranging from 0.1 to 2.9 ..mu..m/min between 750 and 950/sup 0/C. The surface of the coatings showed nodules increasing in size with temperature. The coatings were dense and adherent. The grain size varied with deposition conditions. Often, the grains were too small to resolve optically, but transmission electron microscopy showed the grain size to be very small (2 to 300 nm) and to increase with distance from the substrate. Electron microscopy and x-ray diffraction showed only single-phase TiB/sub 2/, and ion microprobe analysis revealed a constant Ti:B ratio across the coating thickness. Energy-dispersive fluorescence analyses showed more chlorine in coatings deposited at 800/sup 0/C than in coatings deposited at higher temperatures. The Knoop hardnesses of coatings deposited at 800 and 900/sup 0/C were 15 and 33 GPa, respectively. Coatings deposited at 850/sup 0/C or below eroded extensively (up to 30-..mu..m-deep craters during a 1-h test), while those deposited at 900/sup 0/C and above showed very little or no erosion (0 to 2 ..mu..m). 10 references, 11 figures, 3 tables.

• Research Organization: Oak Ridge National Lab., TN (USA)
• DOE Contract Number: AC05-84OR21400
• OSTI ID: 6923900
• Report Number(s): ORNL/TM-9042; ON: DE84010640
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
010404 -- Coal
Lignite
& Peat-- Gasification
010405 -- Coal
Lignite
& Peat-- Hydrogenation & Liquefaction
36 MATERIALS SCIENCE
360205* -- Ceramics
Cermets
& Refractories-- Corrosion & Erosion
BORIDES
BORON CHLORIDES
BORON COMPOUNDS
CHEMICAL ANALYSIS
CHLORIDES
CHLORINE COMPOUNDS
COAL GASIFICATION PLANTS
COAL LIQUEFACTION PLANTS
COATINGS
COHERENT SCATTERING
CORROSIVE EFFECTS
DATA
DIFFRACTION
DISPERSIONS
ELECTRON MICROSCOPY
EROSION
EXPERIMENTAL DATA
FUEL SLURRIES
FUELS
HALIDES
HALOGEN COMPOUNDS
INDUSTRIAL PLANTS
INFORMATION
ION MICROPROBE ANALYSIS
MATERIALS TESTING
MICROANALYSIS
MICROSCOPY
MIXTURES
NONDESTRUCTIVE ANALYSIS
NUMERICAL DATA
SCATTERING
SLURRIES
SUSPENSIONS
TESTING
TITANIUM BORIDES
TITANIUM CHLORIDES
TITANIUM COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
TRANSMISSION ELECTRON MICROSCOPY
VAPOR DEPOSITED COATINGS
X-RAY DIFFRACTION