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

Journal Article · Sun Sep 01 00:00:00 EDT 1985 · J. Electrochem. Soc.; (United States)

DOI:https://doi.org/10.1149/1.2114334· OSTI ID:6407858

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

Erosion- and wear-resistant coatings are needed for numerous applications, including valve and pum 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/sup 0/ 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/sup 0/ 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 (2-300 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 microhardnesses of coatings deposited at 800/sup 0/ 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 1h test), while those deposited at 900/sup 0/C showed very little or no erosion (0-3 ..mu..m).

• Research Organization: Oak Ridge National Laboratory, Metals and Ceramics Division, Oak Ridge, Tennessee
• OSTI ID: 6407858
• Journal Information: J. Electrochem. Soc.; (United States), Journal Name: J. Electrochem. Soc.; (United States) Vol. 132:9; ISSN JESOA
• 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
360201* -- Ceramics
Cermets
& Refractories-- Preparation & Fabrication
360205 -- Ceramics
Cermets
& Refractories-- Corrosion & Erosion
BORIDES
BORON CHLORIDES
BORON COMPOUNDS
CARBIDES
CARBON COMPOUNDS
CHEMICAL ANALYSIS
CHEMICAL BONDS
CHEMICAL COATING
CHEMICAL PREPARATION
CHEMICAL REACTIONS
CHEMICAL VAPOR DEPOSITION
CHLORIDES
CHLORINE
CHLORINE COMPOUNDS
COAL GASIFICATION PLANTS
COAL LIQUEFACTION PLANTS
COATINGS
COHERENT SCATTERING
CONTROL EQUIPMENT
CORROSION PROTECTION
CORROSION RESISTANCE
DEPOSITION
DIFFRACTION
ELECTRON MICROSCOPY
ELEMENTS
EQUIPMENT
EROSION
FLOW REGULATORS
HALIDES
HALOGEN COMPOUNDS
HALOGENS
HARDNESS
HYDROGEN
INDUSTRIAL PLANTS
ION MICROPROBE ANALYSIS
KNOOP HARDNESS
MECHANICAL PROPERTIES
METALS
MICROANALYSIS
MICROHARDNESS
MICROSCOPY
NICKEL
NONDESTRUCTIVE ANALYSIS
NONMETALS
PROTECTIVE COATINGS
PUMPS
REDUCTION
SCATTERING
SURFACE COATING
SYNTHESIS
TEMPERATURE DEPENDENCE
TITANIUM BORIDES
TITANIUM CHLORIDES
TITANIUM COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
TRANSMISSION ELECTRON MICROSCOPY
VALVES
VERY HIGH TEMPERATURE
WEAR RESISTANCE
X-RAY DIFFRACTION