Abstract
Cr3C2-Ni20Cr coatings have been used for corrosion and wear resistant applications. However, one of the shortcomings of these coatings is its low hardness, and consequent low wear resistance, for long term high temperature applications. Nanostructured coatings of many materials have exhibited higher hardness and strength compared with conventional coatings of the same material. Consequently, nanostructured coatings of other materials, including Cr3C2-Ni20Cr have been attempted to enhance overall performance. In this study the effects of high energy milling parameters on Cr3C2-25(Ni20Cr) powder characteristics as well as the microstructure and mechanical properties of nanostructured Cr3C2-25(Ni20Cr) coatings formed by high velocity oxygen fuel (HVOF) spraying have been evaluated. The average particle size and crystallite size of milled Cr3C2-25(Ni20Cr) powders decreased with increase in milling time and this decrease was more pronounced in nitrogen compared to that in hexane. This difference has been attributed to a cushioning effect in the latter medium. The coatings prepared with milled Cr3C2-25(Ni20Cr) powders had a more uniform microstructure, were harder and had higher relative fracture toughness compared with coatings prepared with as-received powders.
Highlights
Coatings containing chromium carbide particles distributed in a nickel-chromium alloy matrix (Cr3C2-NiCr system) have been used for corrosion and wear resistant applications
The hardness of thermal sprayed coatings is affected by the technique as well as characterisctics of the feed stock[2,3,30,31]
In the high velocity oxygen fuel (HVOF) technique, the particle velocity is high and thermal energy low, and this leads to high hardness[32]
Summary
Coatings containing chromium carbide particles distributed in a nickel-chromium alloy matrix (Cr3C2-NiCr system) have been used for corrosion and wear resistant applications. These coatings can be used in corrosive environments at temperatures (up to 900 °C), much higher than that at which the harder WC-Co coatings can be used. Several methods have been used to prepare thermal sprayed nanostructured coatings These include direct spraying of nanosized powders with or without gaseous or liquid precursors and spraying of specially designed alloys with low critical cooling rates[11,12,13,14]. The most widely used method consists of high energy mechanical milling of conventional powders to obtain nanocrystalline powders, which are subsequently agglomerated to the required size prior to spraying[15,16,17,18,19,20]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
