Influence of spray distance on erosion wear resistance of plasma sprayed WC-12Co coating(4)

       Figure 25 The micro morphology of 50 μm (30 mesh) sand grains

2 Results and analysis

2.1 The influence of spraying distance on the phase structure of the coating

Figure 3 shows the XRD patterns of the powder and the coating at different spraying distances.

By comparing the diffraction results of the coatings at different spraying distances, it can be seen that the main component phase of the four coatings is the WC phase, and there are a certain amount of W2C phase and the brittle and hard Co6W6C phase in the coating, indicating that WC has appeared in the coating

Different degrees of oxidative decarburization (2WC+O2→W2C+CO2; 2WC→W2C+CO) generate W2C phase.

By comparing the peak height ratio of W2C main peak (101) crystal plane (2θ=39.6°, d=0.227 nm) and WC main peak (100) crystal plane (2θ=35.7°, d=0.251 nm), Table 3 shows that spray coating

The W2C/WC peak-to-height ratio of the coating at a distance of 120 mm is the largest, and the W2C/WC peak-to-height ratio of the 130 mm and 140 mm coatings is the smallest.

It shows that the decarburization behavior is the most serious when the spraying distance is 120 mm, and the decarburization is the lightest when the spraying distance is 130 mm and 140 mm.

Through EDS analysis, the mass fraction of coating C under different spraying distances were 9.54%, 4.67%, 12.23% and 12.19%, respectively.

When the spraying distance is 120 mm, the mass fraction of coating C is the lowest, which further shows that WC oxidation decarburization is serious.