Experimental and Numerical Study of the Influence of Substrate Surface Preparation on Adhesion Mechanisms of Aluminum Cold Spray Coatings on 300M Steel Substrates

The effect of substrate surface topography on the creation of metallurgical bonds and mechanical anchoring points has been studied for the cold spray deposition of pure aluminum on 300M steel substrate material. The coatings adhesion strength showed a significant decrease from 31.0 +/- 5.7 MPa on polished substrates to 6.9 +/- 2.0 MPa for substrates with roughness of 2.2 +/- 0.5 lm. Strengths in the vicinity of 45 MPa were reached for coatings deposited onto forced pulsed waterjet treated surfaces with roughnesses larger than 33.8 lm. Finite element analysis has confirmed the sole presence of mechanical anchoring in coating adhesion strength for all surface treatment except polished surfaces. Grit embedment has been shown to be non-detrimental to coating adhesion for the current deposited material combination. The particle deformation process during impacts has been studied through finite element analysis using the Preston-Tonks-Wallace (PTW) constitutive model. The obtained equivalent plastic strain (PEEQ), temperature, contact pressure and velocity vector were correlated to the particle ability to form metallurgical bonds. Favorable conditions for metallurgical bonding were found to be highest for particles deposited on polished substrates, as confirmed by fracture surface analysis.