THE CHANGES OF STRUCTURE UPON THERMAL-TREATMENT OF GOLD COATINGS ELECTRODEPOSITED ON VACUUM-SPUTTERED TI AND ELECTRODEPOSITED NI-B OR NI-FELAYERS

The changes in structure and chemical composition of gold coatings aft er thermal treatment in dependence on the composition of metallic laye rs has been studied by transmission electron microscopy, scanning elec tron microscopy and X-ray diffraction (XRD). An electrodeposited gold coating on Ti as well as on Fe-Ni/Cu and Ni-B/Cu systems had no observ able changes in phase composition and structure after thermal treatmen t of 200 h at 150-200 degrees C. Spontaneous growth of gold crystal wh iskers were observed on the gold coating on a Ti substratum (50-100 h, 350 degrees C). There were changed friable structures in some places. XRD data testify a presence of Au2Ti and AuTi3. A changed structure c ontaining big grains developed in some places on the gold coating of t he system Au/Fe-Ni/Cu after thermal treatment (50 h, 350 degrees C). N ickel diffusion and the presence of intermetallic AuCn in the gold coa ting was also observed, The gold coating of the system Au/Ni-B/Cu rema ins stable with respect tb structure and chemical purity. The electrod eposited Ni-B layer (B, 4-8 wt.%; C, 3-7 and 10(-2) wt.% in dependence of the technique of electrodeposition) is amorphous. The gold coating on a Ni-B substratum had no observable changes in structure after a t hermal treatment of 200 h, 350 degrees C.