Influence of Crystal Structure on the Friction and Wear of Titanium and Titanium Alloys in Vacuum
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CENTER
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The friction and wear characteristics were determined in vacuum to 10 to the -9 mm Hg for titanium and titanium alloys sliding on themselves and on 440-C stainless steel. The titanium alloys included titanium-tin, titanium-oxygen, and titanium-zirconium. The influence of tin and oxygen on the lattice parameters of titanium and its friction and wear characteristics were measured. The effect of crystal transformation from a hexagonal to a cubic form for a zirconium-titanium alloy was also studied. Friction and wear experiments were conducted with a hemispherical rider sliding on a flat disk surface at loads to 1000 grams and speeds to 2250 feet per minute. Experiments were conducted at 750 and 4250 F. While most hexagonal metals have good friction and wear properties, the results of this investigation indicate that titanium, although a hexagonal metal, exhibits relatively high friction. This high friction may be related to a difference in the slip mechanisms for titanium titanium unlike most hexagonal metals slips on the lob planes rather than on the 0001 basal plane. The addition of tin or oxygen to titanium expands the crystal lattice of titanium and reduces the friction and wear characteristics. The friction coefficient obtained for a titanium-zirconium alloy markedly increased complete seizure occurred when the material transformed from the hexagonal to the cubic form.
- Metallurgy and Metallography