Laboratory Evaluation

At temperatures below 300°C investigators using Auger spectroscopy and X-ray photoelectron spectroscopy have confirmed the presence of phosphate on the surface of TCP lubricated steel (2,3,4). Products have also been identified as FeP04 and (FeP04.2H20) by the use of electron diffraction (5). Wear surfaces lubricated with TCP containing lubricants were examined by a series of surface analytical instruments (AES, XPS & TEM) and found to contain ferrous phosphate-and an organic polyphosphate (6,7). These authors suggest the ferrous phosphate appears early in the test and continues to increase until it covers the wear surface. The polyphosphate polymer appears to form after the ferrous phosphate reaches a critical surface coverage (8,9).

^Numbers in parenthesis designate reference numbers at the end of the paper.

Reaction products at temperatures above

300°C have not been adequately described in the literature. There is, however, indication that transition metals such as iron provide a low energy path decomposition for TCP in this high temperature region. Recent studies at Penn

State have shown the presence of Fe,P and Fe_C

in vapor deposited TCP on iron foil at 700 C.

Additional studies of vapor deposited TCP films

(10,11,12) have shown the formation of thick films rich in phosphorous. These films appear to be catalyzed by iron and copper containing alloys. The chemical nature of these films has not been completely analyzed for chemical constituents but has been characterized by SEM.

Over the temperature range of 500 to 1000 C it has been found that the higher the temperature the thicker the film formed. The lubricity of thermally formed vapor delivered TCP films has been evaluated by a four-ball wear tester at 370°C.

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