Characterization of cermet coatings deposited by low-pressure cold spraying

Abstract

The paper presents the influence of substrate preparation on low pressure cold sprayed (LPCS) coatings adhesion strength and microhardness. The LPCS process parameters such as: (i) gas temperature; (ii) gas pressure; (iii) gun linear speed; (iv) powder feeding rate; and (v) spray distance were kept constant during deposition. The coatings were sprayed using metallic powders having different morphology, namely spherical (Al, Zn, Sn, Cu) and dendritic (Ni, Cu) with the grain size of about −50+10μm. These powders were mixed with alumina before spraying in a weight ratio of 50:50. Copper and aluminium alloy were used as substrates. The substrate preparation included sand-blasting and grinding. The coating microstructures were characterized by scanning electron microscopy (SEM) and X-ray diffractometry (XRD). The adhesion strengths of coatings were determined by pull-off method and showed that coating adhesion reached 65MPa. The measurements of coatings microhardness were carried out also. Finally, the values of adhesion strength and microhardness of coatings were correlated with the substrate preparation and the microstructure of coatings. The microhardness of LPCS coatings was in the range of 20 to 201HV0.02 and depended mostly on sprayed powder material.