PURPOSE: To treat the surface-hardened layer of an Au alloy member for decoration to extremely high hardness by subjecting an Au alloy member having the compsn. contg. ≥1 kinds among Cr, Ag and Cu and the balance substantially Au and base texture dispersed therein with proeutectic Cr to a nitriding treatment.
CONSTITUTION: An Au alloy member is constituted of a compsn. contg., by wt%, 5W15% Cr, and 3W44% ≥1 kinds of Ag and Cu, and contg. further 0.1W3.0 Al according to need and consisting of the balance Au with unavoidable impurities. Said member is requlated to consists of the texture dispersed uniformly with relatively coarse proeutectic Cr (crystallized in the process of solidification) and finely precipitated Cr (formed after the nitriding treatment) in the base. If the surface of the Au alloy member having such compsn. and texture is subjected to a nitriding treatment, more preferably an ion nitriding treatment, the Au alloy member having the surface hardened layer exhibiting extremely high hardness is obtd.
YOSHIDA HIDEAKI
HIJI TOSHIHARU
MATSUDA FUKUHISA
NAKADA KAZUHIRO
