The effect of gas flow rate on structural, mechanical and antibacterial properties of atmospheric plasma sprayed Cu coatings

Abstract

The Copper (Cu) powder is sprayed on 316L stainless steel surface using an atmospheric plasma spray (APS) system to eliminate infections and bacteria on the surface. Here, the effects of gas flow rate (GFR) on structural, mechanical and antibacterial properties of coatings are investigated. The comparative analysis of coatings created by different gas flow rates of 20, 25, 30 and 35 lmin−1 is performed. The results show that the coating with 20 lmin−1 GFR is thin and too weak due to the disturbance in the thermal pinch and the existing excessive pores. With increasing the GFR, the coating roughness and porosity decrease which in turn increases the hardness and adhesion of the coatings. The connection between flat splats and continuous and uniform layers gets better. The high-quality coating is seen at the GFR of 30 lmin−1 with the adhesion strength and hardness of 4B and 163 HV0.1, respectively. Besides, it shows three and a half and three times increase of antibacterial property after 12 h compared to 316L stainless steel versus PTCC 1112 Staphylococcus aureus and ATCC 10536 Escherichia coli bacteria, respectively. But the coating having a GFR higher than critical value (30 lmin−1) shows discontinuous layers due to the plasma jet divergence and reduction of particles velocity.