Table of Contents
Journal of Metallurgy
Volume 2011, Article ID 802093, 6 pages
http://dx.doi.org/10.1155/2011/802093
Research Article

Process Heating and Postannealing Effects on Microstructure and Hardness of the Sputtered Ni-P-Al Coatings

Department of Materials Science and Engineering, National United University, A2-344R, Lienda, Kung-Ching-Li, Miaoli 36003, Taiwan

Received 1 October 2010; Revised 31 December 2010; Accepted 5 January 2011

Academic Editor: David G. Morris

Copyright © 2011 Yu-Ming Su et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Ternary Ni-P-Al alloy coating was fabricated by magnetron sputtering technique with a Ni-P/Al composite target source. The effects of thermal treatments, including deposition process heating and postannealing, on phase transformation phenomenon and related mechanical properties were investigated. The as-deposited coatings produced under process temperature below 4 7 5 ∘ C showed an amorphous/nanocrystalline microstructure. Significant crystallization of Ni matrix and precipitation of N i π‘₯ P 𝑦 and N i 𝑝 A l π‘ž compounds were observed for the coatings manufactured under high sputtering temperatures above 5 0 0 ∘ C . The amorphous Ni-P-Al coatings were postannealed from 500 to 6 0 0 ∘ C in vacuum environment for comparison. The amorphous feature of the Ni-P-Al coating remained unchanged under a high annealing temperature of 5 5 0 ∘ C , showing a superior thermal stability as compared to those fabricated under high process temperatures. Superior hardness was obtained for the post-annealed Ni-P-Al coatings due to volumetric constraint of crystallization and precipitation. On the other hand, the overaging phenomenon and subsequent degradation in hardness were found for the Ni-P-Al coatings fabricated under high-temperature deposition processes. The phase transformation mechanisms of the coatings through different thermal treatments were intensively discussed.