Materials evaluation of diffusion bonded steel bar and its impact characteristics

• Published in: NDT & E international : independent nondestructive testing and evaluation Vol. 35; no. 4; pp. 263 - 271
• Main Authors: Katoh, Mitsuaki, Nishio, Kazumasa, Yamaguchi, Tomiko
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01-06-2002; Elsevier Science
• Subjects: Acoustical measurements and instrumentation; Acoustics; Analysing. Testing. Standards; Applied sciences; C-scope presentation; Cross-disciplinary physics: materials science; rheology; Diffusion bonding; Exact sciences and technology; Fundamental areas of phenomenology (including applications); Impact test; Materials science; Materials testing; Metals. Metallurgy; Nondestructive testing; Nondestructive testing: ultrasonic testing, photoacoustic testing; Physics; Ratio of non-bonded area; Testing for defects; Transition liquid phase diffusion bonding; Ultrasonic test; C-scope presentation; Ultrasonic test; Diffusion bonding; Impact test; Ratio of non-bonded area; Transition liquid phase diffusion bonding; Immersion test; Acoustic measurement; Welded joint; Ultrasonic control; Roughness; C scan; Mechanical joint; Rough surface; Experimental study; Non destructive test; Diffusion welding
• ISSN: 0963-8695; 1879-1174
• DOI: 10.1016/S0963-8695(01)00059-7

When we apply non-destructive test for evaluating the soundness of weld joints it is necessary to know the mechanical properties of the joints by destructive test. In this paper we tried to obtain the correlation between the data by ultrasonic C-scope method and the absorbed energy by Charpy impact test for diffusion bonded steel bars. The surface roughness of specimens (materials: S25C, mild steel) used for the diffusion bonding was changed into several steps by machining and the diffusion bonding was performed on five kinds of combinations of the surface roughness. Through this process we obtained the diffusion bonds whose ratio of non-bonded area was different. In the ultrasonic test we used the frequency of 10
MHz and a transducer of 12.7
mm in diameter. The ratio of non-bonded area is obtained by using C-scope method by immersion testing, and this depended on the threshold echo level when we binarized the images of C-scope presentation and the surface roughness of the specimen. The lower the threshold echo level, the larger the ratio of non-bonded area. The absorbed energy depended on the ratio of non-bonded area. It is made clear that the proper threshold echo level should be selected for evaluating the soundness of diffusion bonds by ultrasonic test. Moreover, when the transition liquid phase diffusion bonding was performed on SD345 (deformed reinforcing steel bar) using Ni amorphous foil as an insert metal the absorbed energy also decreased with the increase in the ratio of flaw area obtained by ultrasonic test, though no change in the tensile strength was observed.