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Rolling‐Contact Fatigue and Wear of CVD‐SiC with Residual Surface Compression
Author(s) -
Chao LuenYuan,
Lakshminarayanan R.,
Shetty Dinesh K.,
Cutler Raymond A.
Publication year - 1995
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1995.tb08662.x
Subject(s) - materials science , spall , composite material , coating , residual stress , tribology , microstructure , brittleness , compression (physics) , composite number , contact mechanics , structural engineering , finite element method , engineering
The rolling‐contact fatigue life and wear of CVD‐SiC coatings with surface compression were studied using a three‐ ball‐on‐rod rolling‐contact fatigue (RCF) tester. Two levels of surface compression in the coatings, approximately 190 μm thick, were introduced by using substrates of a liquid‐phase sintered SiC and a SiC‐30 vol% TiC to obtain desired thermal‐expansion mismatches with the CVD‐SiC. Residual surface compressions of 250 and 680 MPa were measured in the CVD‐SiC coatings on SiC and SiC‐30 vol% TiC substrates, respectively, by a strain‐gage technique. In the RCF test, the fatigue life of the CVD‐SiC coating with the moderate surface compression was limited by severe wear by a brittle fracture mechanism at a Hertzian contact stress of 5.5 GPa. The CVD‐SiC coating on the SiC‐30 vol% TiC composite, on the other hand, did not show measurable wear. A majority of the tests (11 out of 16) were suspended at 100 h or stopped due to failure of the steel balls. Five tests stopped due to spalling of the CVD‐SiC coating at weak interfaces 10 to 15 μm below the contact surface. Examination of the microstructure of the CVD‐SiC coating in cross sections revealed that the weak interfaces that led to the spalling were related to discontinuous growth of the CVD‐SiC in the form of nodules or growth regions. Elimination of these defective structures is likely to enhance the tribological performance of surface‐toughened CVD‐SiC.