摘要
一些特殊的工件在加工过程中,镀层易起皮、脱落,镀层与基体间有一过渡层可避免这一点,这通常可通过局部热处理加以解决;而传统的扩散退火热处理中,热量是从材料外部向其内部传递,整个材料都被加热,要实现镀层与基体的界面扩散,就会不可避免地造成纳米晶镀层的晶粒长大;而且如果只需对材料的某个局部加热,其效率显然较低。为此,对电沉积纳米晶镍镀层与低碳钢基体进行电阻点焊试验,考察了利用电流作用下界面接触电阻产生热量来实现镀层与基体界面原子扩散的可行性以及对镀层微观结构的影响。用X射线衍射(XRD)表征了点焊前后纳米晶镍镀层微观结构的变化;利用背散射电子像(BSE)观察界面的结构变化;用扫描电子显微镜(SEM)附带的能量色散谱(EDS)探测了界面上的原子扩散。结果表明:点焊前后纳米晶镍镀层的平均晶粒尺寸和织构基本保持不变;镀层和基体界面上发生了明显的原子互扩散,形成了扩散过渡层。该方法既可以促使镀层与基体界面发生原子扩散,又能保证纳米晶镍镀层晶粒不长大,为纳米晶体镀层材料的界面局部热处理提供了一种新的途径。
Resistance spot welding tests were conducted for electrodeposited nanocrystalline Ni coating and carbon steel substrate.The feasibility to realize atomic diffusion at coating-substrate interface by using heat generated via contact resistance at the interface under electric current was investigated,and corresponding effect on the microstructure of the Ni coating was examined.The crystal structure of the nanocrystalline Ni coating before and after spot welding was analyzed by means of X-ray diffraction,and the interface structure was analyzed by means of backscattered electron image.The atomic diffusion at the interface was observed by energy dispersive spectrometry.It was found that the average grain size and texture of Ni coatings remained almost unchanged after spot welding.Obvious inter-diffusion occurred at the coating-substrate interface,generating a diffusion intermediate layer.This route could be well used to accelerate atomic diffusion at coating-substrate interface and prevent nanocrystalline Ni grains from growing up,showing promising application for local interface heat-treatment of nanocrystalline coating.
出处
《材料保护》
CAS
CSCD
北大核心
2011年第3期57-59,73,共4页
Materials Protection
基金
河南工业大学自然科学基金项目(10XZR009)
关键词
界面局部热处理
电阻点焊
纳米晶镍镀层
界面扩散
晶粒长大
织构
local interface heat-treatment
resistance spot welding
nanocrystalline nickel coating
interface diffusion
crystalline growth
texture
