Investigation of Properties and Wear Behavior of HVOF Sprayed TiC-Strengthened Fe Coatings
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JTTEE5 18:672–677 DOI: 10.1007/s11666-009-9384-4 1059-9630/$19.00 ASM International
Investigation of Properties and Wear Behavior of HVOF Sprayed TiC-Strengthened Fe Coatings Kirsten Bobzin, Thomas Schlaefer, Katharina Richardt, Thomas Warda, and Guido Reisel (Submitted September 10, 2008; in revised form January 15, 2009) High-velocity oxyfuel (HVOF) sprayed carbide based coatings (such as Cr3C2/NiCr) are industrially well established for wear protection applications. Due to their high carbide content of typically 75 wt.% and more, they provide very high hardness and excellent wear resistance. Unfortunately, costs for matrix materials such as nickel underlie strong fluctuations and are normally well above the prices for iron. Therefore an alternative concept to conventional carbides is based on TiC-strengthened low-cost Fe-base materials, which are already used for sintering processes. Depending on the carbon content, the Fe-base material can additionally offer a temperable matrix for enhanced wear behavior. The sprayability of TiC-strengthened Fe-powders with a gaseous and a liquid fuel driven HVOF system was investigated in this study. The resulting coatings were analyzed with respect to microstructure, hardness, and phase composition and compared with galvanic hard chrome, NiCrBSi, and Cr3C2/NiCr (80/20) coatings as well as with sintered Fe/TiC reference materials. Furthermore, the Fe/TiC coatings were heat treated to proof the retained temperability of the Fe matrix after thermal spray process. Tribometer tests (pin-on-disk tests) were conducted to determine wear properties.
Keywords
Fe-based coatings, HVOF spraying, TiC reinforcement, wear behavior
1. Introduction Thermal spraying is a well-established technique for application of wear protection coatings. Often carbides (such as Cr3C2/NiCr) are used (Ref 1, 2). Increasing commodity prices of the typical wear protection materials are leading to an increase of coating costs. This can reduce the competitiveness of thermal spraying compared with other coating technologies. A further disadvantage with regard to competitiveness is created when carbide coatings are overdimensioned for the considered application (Ref 3). In this context the substitution of cost-intensive materials is discussed, and often Fe-based materials are mentioned (Ref 4, 5). Modern ferrous-based TiCstrengthened (Fe/TiC) coatings can be a very promising alternative to those carbide materials. With their advantageous wear properties (Ref 6) and lower material costs compared with conventional carbides, influenced by lower commodity prices of the alloy materials, cost-effective wear protection coatings can be realized.
2. Experimental Procedure For a classification of spraying results with TiCstrengthened Fe-based powders, the coatings were compared with the following reference materials and coating systems:
Fe/TiC sinter materials (pressed powder and hard
ened sinter bodies) High-velocity oxyfuel (HVOF) sprayed Cr3C2/NiCr (80/20) coatings HVOF sprayed and remelted NiCrBSi coating
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