Tungsten carbide (WC) is a very hard material that provides excellent wear, abrasion and scratch resistance. It can also shield surfaces from corrosion and erosion. Tungsten carbide coatings are a cost effective alternative to replacing components that have experienced irreparable damage and wear.
The properties of tungsten carbide coatings are determined by the volume fraction of WC particles and their size. The tungsten carbide particles in coatings must be matched to the application in order to achieve the desired performance characteristics. When subjected to cyclic loading, coated articles can fail due to fatigue, which is a progressive failure that culminates in fracture after a number of cycles.
Coatings made by various thermal spray processes were subjected to dry-sand rubber wheel (DSRW), high-speed slurry abrasion and cavitation erosion testing. The results were plotted and the coating hardness was recorded for each sample. Typical hardness values for each spray process are shown in Table 1.
SEM-images of the various samples were also obtained and displayed in Fig. 2. All of the coatings retained their bimodal carbide size distribution. The angular structure of the carbides in the coatings is in agreement with the powder structures and demonstrates that the HVFS system deposits coatings that are very consistent.
During the DSRW and HSSA abrasion tests, all of the coated samples demonstrated a good ability to resist abrasion. The tungsten carbide coatings showed low surface roughness and the abrasion test results are consistent with the coating hardness data.
