Exhaust - Downloaded By[University of Florida At 18:18 27...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
Downloaded By: [University of Florida] At: 18:18 27 February 2008 Lubrication of Silicon Nitride in a Simulated Turbine Exhaust Gas Environment@ W. GREGORY SAWYER (Member, STLE), THIERRY A. BLANCHET (Member, STLE) and SALVADORE J. CALABRESE Rensselaer Polytechnic Institute Dcpartmcnt of Mechanical Engineering, Aeronautical Engineering and Mechanics Troy, New York 12180 7bti17.g hc~s been conducted on silicon nitride (Si3N4) in simulated engine exlin~~st gas environnmzts in four-ball rolling contacts and pi~n-o~r.-disk slidin,g contacts lo 590°C. Utilizing a steel race, the depth (f the wenr tmck formed at the Si3N4/Si3N4 rolling contad in the presence of exhnust gas rum roughly one-hay that formed in the pres- ntce of N2 alone. Deposition of lubricous microctystalline graphite c(~rl,on from CO ruithin the exhaust was conjrmed by Raman spec- troscoj~y. I?emovnl of H20 from the exhaust gas further reduced roll- ing ruear. I<xhaust gm alone provided no benejt to Si3N4/Si3N4 slitting contncts, ruhere the rate of wear greatly exceeds the rate at rohich l~tbrico~~s carbon may deposit from the exhaust environment. As compnre(1 to that memured in the presence of N2 alone, the di- rcctctl ndmixture t$hyyrlrocnrbon (C2H2) to the exhaust gas enhanced the brbricr~tion of Si3Nq with reductions of uj) to 25-JoU in rolling roear, 650-foll in steady-state sliding wear rate and 20-fold in sliding friction. KEY WORDS Silicon Nitride, High Temperature, Gas Turbines INTRODUCTION With demands Tor higher efficiency and thrust-to-weight ~-;~tio, and lcss environmentally damaging emissions, engines with liighcr combustion and operating temperatures are un- tlcr dcvclopmcnt. These temperatures necessitate the adop- tion or ccrarnics as bcaring materials. The low density, high toughness, and thcrmal btability of silicon nitride (Si3N4) rnakc it all cxccllent candidate ceramic (I). Thc limitcd ~cmpcrature range over which currently avail- able liquitl lubricants have useful viscosity and stability pre- vcnu their use in demanding environments (2), such as thosc I'ound in high perrormance turbine engines with esti- mated operating temperatures exceeding 850°C. Replace- ment of fluid with solid third-body particles introduced between contacting surfaces (granular collision or powder lu- brication) has been shown to reduce friction and provide load bearing capabilities and has potential for high temper- ature application (3), (4). Solid lubricants already have a proven ability to lubricate ceramic surfaces over a wide range of temperatures, loads, and sliding speeds (5). The major obstacle with solid lubricants, which are typically employed as thin predeposited films, is their replenishment as they in- evitably wear and are depleted from the contact surfaces. If a composite material with solid lubricant inclusions was to be utilized as one of the contacting bodies, low shear strength surface films could be continuously replenished across the contact interface as wear proceeds. DellaCorte and Sliney (6) have developed composites with complementary Ag and
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 08/22/2011 for the course EGM 4313 taught by Professor Mei during the Spring '08 term at University of Florida.

Page1 / 7

Exhaust - Downloaded By[University of Florida At 18:18 27...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online