浸蚀前处理对锆铜合金表面电铸镍层结合强度的影响

Effect of etching pretreatment on adhesion of Ni coating electroformed on Zr-Cu alloy

采用不同浸蚀液探索锆铜合金前处理工艺,以提高电铸镍层在其表面的结合强度。采用金相显微镜和扫描电子显微镜,考察了锆铜合金试样浸蚀前后的表面形貌。结果发现,样件在47°C的100g/L或200g/L稀硫酸溶液中浸蚀后表面没有明显变化,其表面氧化层不能被完全去除。使用100g/L硫酸+100g/L硫酸铁溶液时,常温(25°C)下已有比较明显的腐蚀作用,但样件表面因腐蚀不均匀而变得凹凸不平。提高该溶液的温度至50℃后,浸蚀3min时基体表面的腐蚀有一定减缓,但仍不均匀,而浸蚀5min时样件表面平整,晶粒状结构凸显。若采用5g氯化铁+50mL盐酸溶液在常温下浸蚀,由于其腐蚀作用较强,不易控制,超过30 s就足以破坏基体表面晶粒的晶格,加剧组织缺陷的形成,不利于电铸层结合力的提高。奥拉法结合强度测试表明,使用上述硫酸+硫酸铁溶液在50℃以下处理3~5 min后,基体与电铸镍层的结合强度可以达到180 MPa以上。

To improve the adhesion of electroformed nickel coating on Zr-Cu alloy,the pretreatment of Zr-Cu alloy with different pickling solutions was studied.The surface morphologies of Zr-Cu alloy before and after being pickled were examined by using metallurgical microscope and scanning electron microscope(SEM).The results showed that the surface of Zr-Cu alloy changed slightly after being pickled at 47℃ with ether a 100 g/L or a 200 g/L H_(2)SO_(4) solution where the oxide film on Zr-Cu alloy surface could not be dissolved completely.The corrosion of Zr-Cu alloy in a 100 g/L H_(2)SO_(4)+100 g/L Fe_(2)(SO_(4))_(3) solution at room temperature(25℃)was obvious and rapid,but uneven,resulting in a rough surface of the substrate.When the temperature of the H_(2)SO_(4)-Fe2(SO_(4))_(3) solution was raised to 50℃,the corrosion of Zr-Cu alloy slowed down within 3 min,whereas some local areas on its surface were corroded severely.However,the Zr-Cu alloy pickled in the H_(2)SO_(4)-Fe_(2)(SO_(4))_(3) solution at 50℃ for 5 min had a smooth surface with the exposure of crystal grains.The pickling in a solution comprising FeCl_(3)5 g and hydrochloric acid 30 mL was difficult to control even at room temperature due to its strong corrosivity.The lattice of grains would be destroyed in this solution over 30 seconds,leading to structural defects on the substrate surface.The result of adhesion test by Ollard method showed that the nickel coating electroformed on the Zr-Cu alloy substrate pickled with the said H_(2)SO_(4)-Fe2(SO_(4))_(3) solution at 50℃ for 3-5 min had an adhesion strength higher than 180 MPa.