Abstract
The addition of a low modulus coating by a spray process was used to improve the fatigue properties of a fillet-welded joint. Fatigue tests were performed on TIG welded cruciform joints in 1Cr18Ni9Ti stainless steel under stress ratio R = 0, in the as welded, flame sprayed, and plasma sprayed conditions. These showed that the plasma spray process was effective in increasing the fatigue strength of the cruciform welded joints, but flame spraying was less effective. In particular, the fatigue strength of the as welded joints was increased by 26 % with plasma sprayed coating, but by only 10 % with the flame sprayed coating. The corresponding increases in fatigue life were 1.58~9.62 for the plasma sprayed specimens compared with 1.55~1.97 times for the flame sprayed specimens. Finite element stress analysis showed that the stress concentration factor at weld toe of the spray coated specimens was much decreased. It also confirmed that the stress perpendicular to the interface between the spray coating and base metal was greater than the adhesion strength of the flamed-sprayed coating, which resulted in the coating near the weld toe peeling off during the fatigue tests. As a result, the fatigue life of the flame sprayed specimens was lower than that of the plasma sprayed ones.
Published Version
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