Effect of process parameters on the formation of Ti–Al coatings fabricated by mechanical milling

Coating of Al substrate by metallic Ni through mechanical alloying

“…3e. The formation of a layered structure implies that plastic deformation increased at further milling times [13]. The cracks, which are shown in Fig.…”

“…Material of the grinding medium, such as Fe, was not detected in the top coating layer; the balls and chamber inner walls were likely coated by a Ni-Al layer in the early stages of the MA processing, which prevented the release of Fe into the coating [10,13]. The magnitude of contamination during MA depends upon the milling time and intensity, nature of the powder, ball-to-powder weight ratio, seal integrity, etc.…”

“…In order to prevent contamination by the atmosphere, milling chamber was completely sealed; if the container is not properly sealed, the atmosphere surrounding the container leaks into the container and contaminates the powder. When the chamber is properly sealed, interstitial contaminants can be reduced to a minimum at the milling stage [13]. The milling times were 20, 50, 80, 120, 200, 300, 420, 720, 1080 and 1500 min.…”

“…1 shows a schematic illustration of the process. The principle of the method is for a substrate and powder to be placed into a rotary chamber along with a number of steel balls [9,13]. When some powder is processed by using MA, part of the milled powder forms a coating film over the milling balls and on the inner wall of the container [8,14].…”

“…When some powder is processed by using MA, part of the milled powder forms a coating film over the milling balls and on the inner wall of the container [8,14]. Due to repeated substrate-to-ball collisions, the powder particles become cold-welded to the surface [13]. Frequent impact of balls has been also used to treat [15,16], activate and harden the surface [17].…”