Microstructure of MoSi2-base nanocomposite coatings formed on Mo substrates by chemical vapor deposition

Abstract The microstructures and formation processes of MoSi2 – Si3N4 or MoSi2 – SiC nanocomposite coatings on Mo substrates by ammonia nitridation or carburizing process followed by chemical vapor deposition of Si was investigated using optical microscopy, field-emission scanning electron microscopy (SEM), cross-sectional transmission electron microscopy (XTEM), and X-ray diffraction (XRD). The present study demonstrated that the crack density formed in the MoSi2-base nanocomposite coatings due to mismatch in the coefficient of thermal expansion (CTE) between the nanocomposite coatings and the Mo substrate could be reduced by the control of volume percentage of the Si3N4 or SiC particles with the low CTE values. Especially, no cracks were observed in the MoSi2-(30– 33) vol.% Si3N4 nanocomposite coating, indicating that its CTE value was close to that of the Mo substrate. The microstructure of MoSi2-base nanocomposite coatings showed the oblate-spheroidal-type Si3N4 or SiC particles dispersed in the equiaxed MoSi2 grains. The average size of equiaxed MoSi2 grains ranged from 300 to 100 nm depending on the processes, and that of Si3N4 or SiC particles ranged from 150 to 90 nm. The growth of MoSi2 grains was inhibited by the nanosize Si3N4 or SiC particles located mostly at the grain boundaries of MoSi2.

[1]  T. Mah,et al.  In Situ Processing and Properties of SiC/MoSi2 Nanocomposites , 2005 .

[2]  Gyeungho Kim,et al.  Growth Kinetics of MoSi2 Coating Formed by a Pack Siliconizing Process , 2004 .

[3]  Gyeungho Kim,et al.  Growth kinetics of three Mo-silicide layers formed by chemical vapor deposition of Si on Mo substrate , 2002 .

[4]  Gyeungho Kim,et al.  Study on reaction and diffusion in the Mo-Si system by ZrO2 marker experiments , 2002 .

[5]  A. Wolfenden,et al.  Experimental investigation of the dynamic elastic modulus and vibration damping in MoSi2-30%Si3N4 as a function of temperature , 2000 .

[6]  Mohan G. Hebsur,et al.  Development and characterization of SiC(f)/MoSi2–Si3N4(p) hybrid composites , 1999 .

[7]  T. Narita,et al.  Siliconizing of Molybdenum Metal in Indium-Silicon Melts , 1998 .

[8]  R. G. Castro,et al.  Elevated temperature mechanical properties of MoSi2/Si3N4, MoSi2/SiC composites produced by self-propagating high temperature synthesis , 1998 .

[9]  J. Takada,et al.  Nitriding of dilute Mo-Ti alloys at a low temperature of 1373 K , 1998 .

[10]  J. Wolfenstine,et al.  The effect of powder processing on the coefficient of thermal expansion of MoSi2-Si3N4 composites , 1997 .

[11]  E. Lavernia,et al.  The effect of Si3N4 on the thermal expansion behavior of MoSi2 , 1997 .

[12]  D. Kum,et al.  Simple procedure for phase identification using convergent beam electron diffraction patterns , 1996, Microscopy research and technique.

[13]  R. Hecht,et al.  Development of continuous-fiber-reinforced MoSi2-base composites , 1992 .

[14]  A. Vasudévan,et al.  A comparative overview of molybdenum disilicide composites , 1992 .

[15]  E. Courtright,et al.  Engineering limitations of MoSi2 coatings , 1992 .

[16]  Charles H. Henager,et al.  Synthesis of a MoSi2SiC composite in situ using a solid state displacement reaction , 1992 .

[17]  Ge Wang,et al.  Deposition and Cyclic Oxidation Behavior of a Protective ( Mo , W ) ( Si , Ge ) 2 Coating on Nb‐Base Alloys , 1992 .

[18]  E. Heikinheimo,et al.  Reactions in the systems MoSi3N4 and NiSi3N4 , 1992 .

[19]  Gd Gerard Rieck,et al.  Phase relations and diffusion paths in the Mo-Si-C system at 1200 degrees C , 1982 .

[20]  K. Sarma,et al.  Interaction of CVD Silicon with Molybdenum Substrates , 1981 .

[21]  J. Hirth,et al.  Mechanism of the solid-state displacement reaction between iron and nickel oxide at 1000°c , 1982 .

[22]  S. Shirasaki,et al.  Nitrogen self‐diffusion in silicon nitride , 1976 .

[23]  R. Perkins,et al.  Development of a fused slurry silicide coating for the protection of tantalum alloys , 1974 .