High-Temperature Galling Characteristics of Ti-6Al-4V with and without Surface Treatments

Journal Article · Sat Jan 01 00:00:00 EST 2011 · Tribology Transactions

DOI:https://doi.org/10.1080/10402004.2010.534837· OSTI ID:1016040

Blau, Peter Julian ^[1]; ERDMAN, III, DONALD L ^[1]; Ohriner, Evan Keith ^[1]; Jolly, Brian C ^[1]

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1. ORNL

Galling is a severe form of surface damage in metals and alloys that typically arises under relatively high normal force, low-sliding speed, and in the absence of effective lubrication. It can lead to macroscopic surface roughening and seizure. The occurrence of galling can be especially problematic in high-temperature applications like diesel engine exhaust gas recirculation system components and adjustable turbocharger vanes, because suitable lubricants may not be available, moisture desorption promotes increased adhesion, and the yield strength of metals decreases with temperature. Oxidation can counteract these effects to some extent by forming lubricative oxide films. Two methods to improve the galling resistance of titanium alloy Ti-6Al-4V were investigated: (a) applying an oxygen diffusion treatment, and (b) creating a metal-matrix composite with TiB2 using a high-intensity infrared heating source. A new, oscillating three-pin-on-flat, high-temperature test method was developed and used to characterize galling behavior relative to a cobalt-based alloy (Stellite 6B ). The magnitude of the oscillating torque, the surface roughness, and observations of surface damage were used as measures of galling resistance. Owing to the formation of lubricative oxide films, the galling resistance of the Ti-alloy at 485o C, even non-treated, was considerably better than it was at room temperature. The IR-formed composite displayed reduced surface damage and lower torque than the substrate titanium alloy.

• Research Organization: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE Laboratory Directed Research and Development (LDRD) Program
• DOE Contract Number: DE-AC05-00OR22725
• OSTI ID: 1016040
• Journal Information: Tribology Transactions, Vol. 54, Issue 2; ISSN 1040--2004
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
33 ADVANCED PROPULSION SYSTEMS
ADHESION
ALLOYS
DESORPTION
DIESEL ENGINES
DIFFUSION
EXHAUST RECIRCULATION SYSTEMS
HEATING
LUBRICANTS
LUBRICATION
OXIDATION
OXIDES
OXYGEN
STELLITE
SUBSTRATES
SURFACE TREATMENTS
TITANIUM ALLOYS
TORQUE
TURBOCHARGERS
VANES
YIELD STRENGTH
titanium
galling
surface treatment