Heat Treatment Effect on the Fatigue Characteristics of Additive Manufactured Stainless Steel 316L

摘要

Stainless steel is an age old and popular alloy known for its high corrosion resistance. This paper is an attempt to explore ways to enhance the fatigue characteristics using heat treatment. The additive manufacturing technique used in this paper is based on Selective Laser Melting (SLM). The material used in this paper is SLM Stainless steel 316L. The specimen printed using SLM technique are subjected to low cycle fatigue tests as per the ASTM standards. Out of the twelve printed specimens, two sets for as-built and heat-treated were separated. A set of six was heat-treated at recrystallisation temperature of 700o C for 2 hours and air cooled. Two specimen each for the as-built and heat-treated category were reserved for tensile testing to evaluate the yield strength, ultimate tensile strength and strain. The remaining eight printed specimen of as-built and heat-treated were allotted for fatigue testing (four each of as-built and heat-treated). After tensile tests, fatigue tests were conducted on the specimens at mean stress equals to 75%, 70%, 65% and 60% of tensile strength, keeping stress ratio, r = 0.5 and at frequency of 5 Hz. Number of cycles to failure were obtained for each specimen for similar loading conditions to plot the S-N curve. The paper concludes by making an analogy in the fatigue characteristic of as-built and heat-treated specimen.