Study of Improvement of Fatigue Properties of Welded Joints by Compressive Stress Induced by Plasma Spraying
Tóm tắt
In order to increase the fatigue strengths of welded joints, a new kind of metal powder spray was developed based on the volume expansion principle, such that the coating would be left in residual compression. Fatigue tests were performed on cruciform welded joints and plates with longitudinal fillet welded attachments in 1Cr18Ni9Ti stainless steel under stress ratio R = 0.1. The specimens were tested in the as-welded condition and after being plasma sprayed with low carbon steel or low transformation temperature metal powder spray. Previous results had indicated that plasma spraying was an effective improvement technique, producing a clear increase in fatigue life over the range of the S-N curve. When the new metal powder spray was used, the improvement was even higher. Compared with specimens sprayed with low carbon steel, the increase in fatigue strength at 2 × 106 cycles and fatigue life over the range investigated of the new metal powder spray were 3.6 to 5.3 % and 16 to 63 % respectively. The extra improvement in fatigue properties was attributed to the presence of a compressive residual stress in the coating.
Tài liệu tham khảo
Whitman J.G., Webber D.: The problem of cumulative damage in welded structures, Weld. Inst. Conf. on Fatigue of Welded Structures, 1970, 7.
Gurney T.R.: Influence of overlays on stresses in fillet-welded joints, Journal of Strain Analysis, 1977, 12, 1, pp. 16–22.
Chadwick M.D.: Influence of low-modulus weld toe overlays on fatigue life, Metal Construction and British Welding Journal, 1973, 9, pp. 330–335.
Gurney T.R.: Exploratory fatigue tests on plastics coated specimens, British Welding Journal, 1963, 10, pp. 530–533.
Nguyen T.N.: The effect of weld geometry and residual stresses on the fatigue of welded joints under combined loading, Journal of Materials Processing Technology, 1998, 77, pp. 201–208.
Branco C.M., Maddox S.J.: Fatigue performance of tungsten inert gas (TIG) and plasma welds in thin sections, International Journal of Fatigue, 1999, 21, pp. 587–601
Huo L.: Preliminary study of improvement of fatigue properties of welded joints by plasma spray process, Doc. IIW-1736-06 (ex doc. XIII-2048–05), Welding in the World, 2006, Vol. 50, No. 7/8, pp. 58–63.
Wang W.: New developed welding electrode for improving the fatigue strength of joints, Journal of Materials Science & Technology, 2002, 18, 6, pp. 527–531.