Fatigue properties improvement of welded structures by plasma spraying process

The plasma spraying process was used to improve fatigue properties of stainless steel 1Cr18Ni9Ti welded joints.Low carbon steel powder was used.The microhardness and coating-substrate adhesive strengths were measured.The fatigue tests of the cruciform joints welded by TIG welding and longitudinal joints welded by arcwelding under tensile load(R=0)were carried out at the welding and spraying conditions.Tests results show that the microhardness and coating-substrate adhesive strengths of plasma sprayed coatings are approximately 1 times larger than that of flame sprayed coatings. Plasma spraying process is effective to improve fatigue life of welded joints.For the cruciform joints, the fatigue strength of the welded specimens is 169.8 MPa, and that of the flame sprayed and plasma sprayed specimens are 186.2 MPa and 213.8 MPa, respectively. The fatigue strength of the plasma sprayed specimens has been increased by 25.9%, and that of the flame sprayed has been increased by 9.7%.For the longitudinal joints, the fatigue strength of the as welded specimens is 91.1 MPa, and that of the plasma sprayed specimens are 100.4 MPa, which is increased by 10.2%.