The Study of the Grit-Blasting Parameters and Their Effects on the Adhesive Strength of the Plasma Sprayed Coatings

摘要

Surface preparation is very important in adhesive bonding of spray coatings to the surface of a workpiece. The common practice is grit-blasting of the surface before subjecting it to the spray coating process. In thisstudy, grit-blasting of an AISI 4130 steel (of different heat treatments) with Al_2O_3 particles was studied and themean roughness (Ra) of the grit-blasted surfaces were then measured. The results show that variations of workingdistance, air pressure and blasting time significantly affect the resultant surface roughness. The results also showthat a 90° blasting angle gives slightly higher Ra but a significantly higher amount of grit residue, in comparisonwith the results obtained for a blasting angle of 45°. After grit-blasting, the specimens were plasma spray coatedwith 80% ZrO_2 -20% Y_2O_3 powder. The adhesive strength of the coating to the substrate was then measuredaccording to the DIN 50160 standard. The results show that for a certain base metal, the adhesive strength isdirectly related to the surface roughness and hardness of the base material.