A new strategy for strengthening additively manufactured cold spray deposits through in-process densification

Abstract

In this study, a novel strategy for strengthening additively manufactured cold spray deposits is proposed, based on a rather under-explored niche of the processing parameters space. We have shown that a combination of two factors (a wide particle size distribution of the feedstock powder and low processing parameters) triggered a successful implementation of this strategy. At such conditions, a significant proportion of the particles (particularly those with a large size) fail to deposit and rebound after their impact instead, initiating the in-process densification effect: by accepting a small price increase trade-off (the wide range powders are inexpensive), the rebounds result in a severe accumulative plastic deformation of the deposited particles and further reduction in porosity. These, in turn, lead to mechanical properties comparable to those produced under high processing parameters (i.e., using N2 gas at high temperatures or using expensive and unsustainable He as the propulsive gas). As a welcome benefit, the detrimental thermal effects encountered in cold spraying using high-temperature processing gas (such as oxidation, nitridation and phase changes) can be effectively minimized using the new low parameters strategy. Overall, the aim of this study is to propose a new manufacturing strategy to fabricate high-performance cold sprayed deposits without the use of expensive and unsustainable He gas.