| Abstract: |
Tungsten carbide in nickel based self-fluxing alloy overlays has been dominating hardfacing applications due to its excellent properties, namely extremely high wear resistance. All possible combinations of particle sizes, morphologies, types of tungsten carbide and matrix chemistries have been tried and virtually no stone was left unturned in attempt to use its full potential. The result of this effort is an immensely successful material platform that addresses a plethora of service conditions. Nevertheless, there are still applications and limits which tungsten carbide has not conquered. Tungsten carbide tends to suffer from extensive degradation during the weld cladding process. It has inferior thermodynamic stability compared to many other industrial carbides, which prevents it from use in high alloyed matrices; its temperature capability is only up to about 500° C and it is heavy and its price is volatile. Mostly in the mining industry, there is a growing demand for even more wear resistant and cheaper overlays as well as overlays for niche applications where tungsten carbide currently cannot be used but its wear resistance is needed. Tungsten carbide virtually reached its limits and if those limits are to be crossed it is important to investigate other materials which would be able to achieve results beyond those of tungsten carbide. The major roadblock for using other hard phases in hardfacing was availability of coarse, dense carbides suitable for hardfacing. These carbides have become recently available and new overlay compositions containing new alloyed carbides and diamonds have been tested for PTA, laser and spray fuse hardfacing applications to alleviate some of the limitations associated with the nickel-based tungsten carbide overlays. This study focuses on (WTi)C which was tested with several matrix materials and tested in wear, corrosion and impact resistance and benchmarked with tungsten carbide. Results for several other carbides such as (WNb)C, (WV)C, and TiC overlays deposited by plasma transferred arc, spray/fuse, and laser cladding will be presented and discussed. As a result of deposition trials and overlay testing, it was found that better thermodynamic stability of alloyed carbides allows them to be used in iron based matrix and/or matrix with a high chromium content, in applications requiring improved corrosion and oxidation resistance, better impact resistance and lower weight.
|
|
