Mechanical and tribological properties of cold sprayed composite Al-B4C coatings

Impact Deposition Behavior of Al/B4C Cold-Sprayed Composite Coatings: Understanding the Role of Porosity on Particle Retention

“…In addition, the effect of the particle material type on the plastic strain will be briefly discussed. Prior to presenting these results, it is worth noting that the model developed in this study is challenging to experimentally validate with in situ deposition data given the small scale of the particles and pores [ 2 , 11 , 12 , 28 , 33 ], and high speeds of the impact deposition process [ 12 , 28 ]. Regardless, we attempt to demonstrate how our model aligns with previous published works.…”

“…Figure 4 c shows the combined effect of both pore sizes (1, 2, 3, and 4 m) and impacting velocities (500, 600, and 700 m/s) on the penetration depth with a pore embedded at a depth of 0.4 into the substrate. The particle size is taken as = 15 m. The pore depth of 0.4 is selected based on the literature [ 12 , 28 ] because there is no noticeable change in behavior for penetration depths in the range of 0.4 to 1 , while no clear trend is observed for the range of 0.1 to 0.3 . In Figure 4 c, it is observed that higher impact velocities result in deeper penetrations in all cases with different pore diameters, and this is expected due to higher kinetic energy [ 19 ], and numerically demonstrated in the literature [ 43 ] that the higher impact velocities of the particle result in deeper penetrations.…”

“…In this study, simulations are performed over the first 24 ns of impact, which is sufficient to allow for observed behavior to be completed; this also corresponds to before when the elastic wave is reflected from the rear of the substrate to return to the impact zone [ 69 ]). In addition, the pore shape is assumed to be spherical to simplify the simulation, and the pore diameters are selected to be 1, 2, 3, and 4 m. Pore depths are 0.1 –0.5 based on the observation made in microscopic images of Al/B C composites from the literature [ 2 , 11 , 12 , 28 , 33 , 70 ]. Lastly, Figure 1 also demonstrates the meshed particle and substrate with refined areas near the contact region.…”

“…During the cold spray process, porosity is an indicator of quality because uncontrolled porosity can result in friable structures and, subsequently, poor mechanical properties [ 26 , 27 ]. In cold spraying, deposition parameters (e.g., temperature and velocity of the gas, standoff distance, and angle of spraying [ 21 ]) and particle morphology (size, shape, type of particles) significantly affect the porosity level in the final coating [ 28 ]. To date, limited studies have focused on exploring the effect of porosity on the mechanical properties and structural integrity of Al/B C coatings [ 27 , 29 , 30 , 31 , 32 ].…”

“…They found that the smaller Al size facilitated the B C retention because of the grain refinement of the coatings, which also improved its wear resistance. In another study, Shikalov et al [ 28 ] studied the tribological behavior of Al/B C coatings for different B C powder sizes (17 and 75 m) and volume percentages, and they found that the higher hardness was attributed to the finer particles, and the B C size had no effect on the adhesion strength. Moreover, other studies [ 12 , 21 ] have shown that hard ceramic particles (e.g., B C) fragment more after deposition into softer materials (e.g., Al), resulting in interfacial gaps between the particles and substrate, and subsequently, increasing the porosity level.…”