Fabrication and Characterization of Ni-SiC Nanocomposite Coatings on Al Substrates by Ball Impact Deposition Method
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ODUCTION
THE mechanical alloying technique has been extensively used for synthesis of a large variety of metal matrix composite powders.[1–3] Mechanical attrition treatment involving successive impacts of the high-energy flying balls to the surface of bulk samples has also been employed to induce grain refinement and consequently surface hardening.[4] Numerous studies in recent years, a selection of which are cited below, have shown that the combination of the above two mentioned processes can be used to mechanically deposit particulate materials on the surface of a metal substrate. The method, hereafter referred to as ball impact deposition (BID), is a green and sustainable technique
ARASH YAZDANI and ALIREZA ZAKERI are with the School of Metallurgy and Materials Engineering, Iran University of Science and Technology, Narmak, Tehran 16846-13114, Iran. Contact e-mail: [email protected] Manuscript submitted September 30, 2016.
METALLURGICAL AND MATERIALS TRANSACTIONS A
that can fabricate advanced coatings with minimal energy consumption and environmental impact. A unique feature of the process is that it enhances the bonding strength between activated particles of the coating material and the substrate due to the cold welding phenomena.[5] BID processes can be classified by type of mill used. Planetary,[5] mechanical vibration,[6] and ultrasonic vibration ball mills[7] as well as SPEX mixer mill[8] have been employed for this purpose. Different target substrates such as milling balls,[5,9] the inner wall of the container,[10,11] a small sample loaded into the vial,[12–15] and plates fixed at the inner top or the inner bottom of the vial[16,17] have been investigated. It is noteworthy that in most studies, either a single metal powder such as Al,[15] Cu,[5] Cr,[11] and Ni,[13] or mixtures of metal powders such as Cr-Al,[18] Ti-Al,[14] Ti-Cr,[11] Ti-Cu,[11] Zr-Ti,[8] W-Cu,[19] Ti-Al-Si,[14] Ti-Al-W-C,[14] and Ti-Cu-Al[10] have been used as the source of coating material. Ceramic powders such as hydroxyapatite,[6] SiC,[20] and TiN[7] have also been employed as the charge material. To the authors’ knowledge, there is no report on the fabrication of a composite coating, comprising
Table I. Ni:SiC Weight Ratio Ni (wt pct) SiC (wt pct)
Composition of the Starting Ni-SiC Charge Mixtures Used in the Study
0
1:20
1:16
1:12
1:8
1:4
1:1
2:1
4:1
6:1
8:1
10:1
12:1
14:1
16:1
18:1
¥
0 100
4.76 95.24
5.9 94.1
7.7 92.3
11.1 88.9
20 80
50 50
66.7 33.3
80 20
85.7 14.3
88.9 11.1
90.9 9.1
92.3 7.7
93.3 6.7
94.1 5.9
94.7 5.3
100 0
reinforcing ceramic particles embodied in a metal matrix, by using only the BID technique. Ni matrix coatings reinforced with SiC particles, due to their improved mechanical and tribological properties, have been deeply investigated and successfully commercialized for the protection of friction parts, such as inside of cylinders in the automotive industry and casting molds.[21,22] Electrodeposition is the most common method for the preparation of Ni-SiC coatings. The depositio
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