Investigations on the fabrication and erosion behavior of the composite diamond coated nozzles

In the present study, adopting the optimized deposition parameters determined by orthogonal simulations, high-quality boron-doped and undoped composite diamond (BD-UCD) films with uniform thickness are deposited on both the inner hole and conical surfaces of the SiC nozzles used in the spray drying equipment. The erosion behavior of the novel diamond film is firstly evaluated in an air-sand erosion rig, with single-layer boron-doped diamond (BDD) and undoped diamond films as comparisons. Thereafter, the erosive wear performance of the BD-UCD coated nozzles is further studied under the industrial condition. The results show that the BD-UCD film exhibits an apparent increase in the erosion resistance over the other two types of diamond films. The mechanism responsible is found to be that the surface undoped diamond layer in the BD-UCD film has outstanding hardness, and boron doping can improve the adhesion between the underlying BDD layer and the substrate. Moreover, under the industrial condition, the ethylene catalytic cracking catalyzers produced with the BD-UCD coated nozzles have much more stable quality than those produced with the uncoated nozzles owing to the aperture stability of the inner hole, further proving the high erosion resistance of the BD-UCD protecting coatings.