Bristle Blasting Surface Preparation in Thermal Spraying

Abstract

The adhesive strength to the substrate plays an important role in the performance of thermal-sprayed coatings and could determine the coating’s service life. It depends to a large extent on the state of the substrate surface prior to coating deposition. In this work, a novel surface pretreatment technique was introduced to thermal spraying, namely, bristle blasting. The adhesive strengths of a plasma-sprayed metallic coating (Ni5Al) and a ceramic coating (Al2O3) were examined and compared to that of coatings sprayed with conventional grit blasting surface pretreatment. A mild steel and an aluminum alloy were selected as substrate materials. The results indicated that bristle blasting could be a practical solution for steel and aluminum alloys when grit blasting is not applicable on site. The adhesion of the sprayed coatings with different pretreatments increased sequentially from mechanical grinding, bristle blasting to grit blasting. The adhesive strength of the Ni5Al coating deposited on the bristle-blasted substrate reached 60% of the adhesive strength of a coating deposited with the traditional grit-blasting pretreatment, while for the alumina coating, it was only about 30%. Moreover, the effect of substrate materials should be considered when using bristle blasting as a surface preparation.