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Title: M 5Si 3(M=Ti, Nb, Mo) Based Transition-Metal Silicides for High Temperature Applications

Abstract

Transition metal silicides are being considered for future engine turbine components at temperatures up to 1600 C. Although significant improvement in high temperature strength, room temperature fracture toughness has been realized in the past decade, further improvement in oxidation resistance is needed. Oxidation mechanism of Ti 5Si 3-based alloys was investigated. Oxidation behavior of Ti 5Si 3-based alloy strongly depends on the atmosphere. Presence of Nitrogen alters the oxidation behavior of Ti 5Si 3 by nucleation and growth of nitride subscale. Ti 5Si 3.2and Ti 5Si 3C 0.5 alloys exhibited an excellent oxidation resistance in nitrogen bearing atmosphere due to limited dissolution of nitrogen and increased Si/Ti activity ratio. MoSi 2 coating developed by pack cementation to protect Mo-based Mo-Si-B composites was found to be effective up to 1500 C. Shifting coating composition to T1+T2+Mo 3Si region showed the possibility to extend the coating lifetime above 1500 C by more than ten times via formation of slow growing Mo 3Si or T2 interlayer without sacrificing the oxidation resistance of the coating. The phase equilibria in the Nb-rich portion of Nb-B system has been evaluated experimentally using metallographic analysis and differential thermal analyzer (DTA). It was shown that Nb ss (solidmore » solution) and NbB are the only two primary phases in the 0-40 at.% B composition range, and the eutectic reaction L {leftrightarrow} Nb SS + NbB was determined to occur at 2104 ± 5 C by DTA.« less

Authors:
 [1]
  1. Iowa State Univ., Ames, IA (United States)
Publication Date:
Research Org.:
Ames Lab., Ames, IA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
933031
Report Number(s):
IS-T 2491
TRN: US200814%%818
DOE Contract Number:  
AC02-07CH11358
Resource Type:
Thesis/Dissertation
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ALLOYS; BEARINGS; COATINGS; DISSOLUTION; ENGINES; EUTECTICS; FRACTURE PROPERTIES; LIFETIME; NITRIDES; NITROGEN; NUCLEATION; OXIDATION; SILICIDES; TRANSITION ELEMENTS; TURBINES

Citation Formats

Tang, Zhihong. M5Si3(M=Ti, Nb, Mo) Based Transition-Metal Silicides for High Temperature Applications. United States: N. p., 2007. Web. doi:10.2172/933031.
Tang, Zhihong. M5Si3(M=Ti, Nb, Mo) Based Transition-Metal Silicides for High Temperature Applications. United States. doi:10.2172/933031.
Tang, Zhihong. Mon . "M5Si3(M=Ti, Nb, Mo) Based Transition-Metal Silicides for High Temperature Applications". United States. doi:10.2172/933031. https://www.osti.gov/servlets/purl/933031.
@article{osti_933031,
title = {M5Si3(M=Ti, Nb, Mo) Based Transition-Metal Silicides for High Temperature Applications},
author = {Tang, Zhihong},
abstractNote = {Transition metal silicides are being considered for future engine turbine components at temperatures up to 1600 C. Although significant improvement in high temperature strength, room temperature fracture toughness has been realized in the past decade, further improvement in oxidation resistance is needed. Oxidation mechanism of Ti5Si3-based alloys was investigated. Oxidation behavior of Ti5Si3-based alloy strongly depends on the atmosphere. Presence of Nitrogen alters the oxidation behavior of Ti5Si3 by nucleation and growth of nitride subscale. Ti5Si3.2and Ti5Si3C0.5 alloys exhibited an excellent oxidation resistance in nitrogen bearing atmosphere due to limited dissolution of nitrogen and increased Si/Ti activity ratio. MoSi2 coating developed by pack cementation to protect Mo-based Mo-Si-B composites was found to be effective up to 1500 C. Shifting coating composition to T1+T2+Mo3Si region showed the possibility to extend the coating lifetime above 1500 C by more than ten times via formation of slow growing Mo3Si or T2 interlayer without sacrificing the oxidation resistance of the coating. The phase equilibria in the Nb-rich portion of Nb-B system has been evaluated experimentally using metallographic analysis and differential thermal analyzer (DTA). It was shown that Nbss (solid solution) and NbB are the only two primary phases in the 0-40 at.% B composition range, and the eutectic reaction L {leftrightarrow} NbSS + NbB was determined to occur at 2104 ± 5 C by DTA.},
doi = {10.2172/933031},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}

Thesis/Dissertation:
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