The effect of cold sprayed coatings on the mechanical properties of AZ91D magnesium alloys

Abstract

Although many previous studies have confirmed that cold sprayed Al+xAl 2 O 3 (x=0-75vol.%) composite coatings on magnesium alloys can effectively improve wear and corrosion resistance, the effect of such coatings on tensile and fatigue properties is still unclear. The present work aims to evaluate the tensile properties and fatigue resistance of an AZ91D alloy with cold sprayed Al+xAl 2 O 3 (x=0, 30, 50vol.%) coatings. The experimental results showed that although the cold spray coating leads to an increase in yield strength and fatigue limit, the tensile strength is reduced. In-situ examination of the macro-morphology of surfaces of the coated specimens during tensile testing was carried out through video recording. It indicated that once the tensile specimens have yielded, horizontal cracks that were perpendicular to the tensile axis formed on the surface of the specimens. Fractographic analysis of the fracture surfaces of the tensile specimens in a scanning electron microscope revealed that all the cracks within the cold sprayed coatings were suspended at the coating/substrate interface. Based on these experimental observations, it is considered that the improved yield strength is attributed to the constraint effect of the cold sprayed composite coatings on the magnesium substrate. The enhanced fatigue limit is a result of the higher yield strength and the coating/substrate interface barrier to crack propagation. The decrease in tensile strength is attributed to the brittle fracture of the cold sprayed coatings when yielding of the specimens.

Effect of coating thickness on microstructure, mechanical properties and fracture behaviour of cold sprayed Ti6Al4V coatings on Ti6Al4V substrates

“…fracture [53]. The maximum flexural stresses before failure for the uncoated substrate and the 0.1 and 0.5 mm thick coatings are 2150 (reported work for CP-Ti is 1850 MPa [54]), 1950 and 1285 MPa, respectively, corresponding to respective the flexural strains of 8.8, 5.6 and 6.3%.…”

Fatigue behavior of cold spray coatings: The effect of conventional and severe shot peening as pre-/post-treatment

“…However, contradictory reports are available on the fatigue behavior of CS coatings of different materials (e.g. Ti [10], Al and its alloys [11] and Mg [12]). Furthermore, the approach typically used to assess the fatigue behavior of CS coated components does not impose a realistic condition on the interface between the coating and the substrate.…”

An Impact of the Recent Developments in Coating Materials and Techniques on the Corrosion Response of AZ91D Alloy: A Review

“…[77][78][79] Comparatively, sol-gel coatings can easily be applied to large surfaces with better uniformity. The composite materials coated AZ91D alloy has been explored for many applications, [80][81][82][83][84][85][86] which is schematically represented in Figure 8.…”

“…The process parameters, like velocity, temperature, density, particle size, must be appropriately balanced to achieve the desired coating thickness on the AZ91D substrate. [84] Yao et al [99] coated the AZ91D surface with Zn-HA/Zn double-layer using the cold spray method, where nitrogen was used as a primary gas. A 20 mm spray distance, 420 °C gas temperature, and 2.3 MPa pressure were considered the optimum coating parameters.…”