不同水基磁悬液对不同厚度涂覆层试块近表面裂纹的磁粉检测

Magnetic Particle Testing of Near Surface Cracks for Different Thickness Coatings Block by Different Water-based Magnetic Fluids

用化学共沉淀法制备平均粒径约为18nm的Fe3O4水基磁悬液,并用XRD(X射线衍射)、TEM(透射电镜)、VSM(磁滞回线)测试手段进行了表征。利用锯床加工、焊接、打磨等工序制作不同厚度带裂纹缺陷涂覆层的人工试块;并分别用纳米Fe3O4水基磁悬液和HR-1型红磁膏配置的水基磁悬液,对制作的含裂纹缺陷试块进行磁粉检测。结果表明:随着涂覆层厚度的增大,使用纳米Fe3O4磁悬液和常规HR-1型红磁膏进行检测所得的磁痕均由密实变得稀疏;涂覆层厚度较小时,纳米Fe3O4磁悬液的磁痕清晰度稍优于常规HR-1型红磁膏的磁痕清晰度;涂覆层厚度较大时,外加磁场施加过程中,纳米Fe3O4磁悬液的磁痕清晰度稍优于常规HR-1型红磁膏的磁痕清晰度;但外加磁场撤离后,纳米Fe3O4磁悬液的磁痕显示变得松散、不连续,显示效果不如常规HR-1型红磁膏。

Fe3O4 water-based magnetic fluid of averaged particle diameter 18 nm was prepared by chemical coprecipitation and characterized by TEM,VSM and XRD.Test block with a coating artificial crack for different thickness coatings was constructed by machining,welding and grinding processing and so on.We used nano-Fe3O4 magnetic fluids and water-based magnetic HR-1red magnetic paste that can be bought in the market to the magnetic particle testing of crack defects block,the result shows：with the coating thickness increasing,the magnetic image of both using nano-Fe3O4 magnetic particle and HR-1 magnetic paste was changed as from being dense to being thinning.At the relatively thin coating location,nano-Fe3O4 magnetic image resolution was a bit better than the conventional HR-1red magnetic paste,but at the thicker location,nano-Fe3O4 magnetic image was slightly superior to the conventional HR-1red magnetic paste while applying an extra magnetic field,but when the magnetic field was moved away,nano-Fe3O4 magnetic image became loose,discontinuous,so the display effect was no better than conventional HR-1red magnetic paste.