The Structure and Phase Transformation Behaviour of Laser Melted Electroless Ni-P Coating on Al after various Tempering Treatments
Chengyun Cui, Jiandong Hu, Yue Yang, Hongying Wang and Zuoxing Guo
The structure and phase transformation behaviour of as-deposited and tempered Ni-P deposits on an Al alloy after laser irradiation were investigated. The binary Ni-P coatings were produced by the electroless deposit technique on the Al substrate. The as-deposited amorphous Ni-P thin films were crystallized after Nd:YAG pulsed laser irradiation. After 300 &Mac176;C heat treatment, various NixPy compounds, including Ni5P2 and Ni3P, formed within the recrystallized Ni matrix. Heat treatment temperatures above 400 &Mac176;C produced NipAlq hard phases (Al3Ni and Al4Ni3), which were observed in the Ni-P-Al coating. The increase in the grain size as the tempering temperature rose from 300 to 500 &Mac176;C due to the formation of NixPy and NipAlq compounds was evident by TEM analysis.