Growth morphologies and mechanism of TiC in the laser surface alloyed coating on the substrate of TiAl intermetallics

• Published in: Journal of alloys and compounds Vol. 351; no. 1; pp. 304 - 308
• Main Authors: Chen, Y., Wang, H.M.
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 10.03.2003; Elsevier
• Subjects: Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Growth mechanism; Growth morphology; Laser deposition; Laser surface alloying; Materials science; MC carbide; Methods of crystal growth; physics of crystal growth; Methods of deposition of films and coatings; film growth and epitaxy; Phase diagrams and microstructures developed by solidification and solid-solid phase transformations; Physics; Solidification; Theory and models of crystal growth; physics of crystal growth, crystal morphology and orientation; Growth morphology; MC carbide; Growth mechanism; Laser surface alloying; Strengthening; Intermetallic compounds; Metal matrix composite; Laser deposition; Binary compounds; Surface alloying; Experimental study; Faceting; Solidification; Composite materials; Composite coating; Titanium carbides; Microstructure; Dendritic structure
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/S0925-8388(02)01077-0

TiC-type MC carbide is an important constituent and strengthening phase for nickel-base superalloys, metal matrix composites (MMCs) and intermetallic matrix composites (IMCs). Its growth morphology, size and distribution have a strong effect on the mechanical properties of materials. In addition, TiC carbide is a typical faceted crystal due to its high Jackson factor. Therefore, the solidification behavior of TiC carbide is an important research subject. In the present study, TiC reinforced composite coatings on the surface of intermetallic alloy γ-TiAl were successfully synthesized by means of laser surface alloying, the growth mechanism and phase morphologies of TiC were investigated as a function of solidification cooling rate. The growth morphology of TiC solidified at a cooling rate of 1.0×10 2 K/s is found to be dendritic, having a platelet/catenulate growth characteristic on dendrite arms. As the solidification cooling rate increases to 2.2×10 2 K/s, the growth morphology of TiC changes to a well-developed dendrite having a three-dimensional network growth characteristic. In spite of the variety of growth morphologies under different solidification conditions, TiC still grows by the lateral growth mechanism. Moreover, the growth kinetics of TiC/Al 3Ti eutectic plays an important role in controlling the carbide growth morphologies.