The influence of Al2O3 reinforcement on the properties of stainless steel cold spray coatings

The effect of Al2O3 additions to type 316 austenitic stainless steel cold spray coatings was studied. Adding Al2O3 to the feedstock powder increased the overall deposition efficiency, though the Al2O3 itself deposited less efficiently than the stainless steel. Shear testing of the coatings using a shear lug test revealed a change in fracture from cohesive to adhesive with increasing alumina addition. The corrosion behaviour, assessed using anodic polarisation tests of the coatings, showed a shift towards the polarisation behaviour of bulk stainless steel with Al2O3 additions. All of these changes in coating behaviour with Al2O3 additions suggest an improved degree of metallurgical bonding, likely due to increased plasticity in the stainless steel particles. With the largest Al2O3 addition the hardness of the layer increased by 30%, but the corresponding wear rate in ball-on-disc testing reduced by a factor often. This suggests a change in wear mode from partially adhesive to abrasive. (C) 2012 Elsevier B.V. All rights reserved.