Overview of Properties, Features and Developments of PM HIP 316L and 316LN

PM HIP 316L is an alloy that is of increased intere st for nuclear applications since its recent ASME code case approval. Over the years, com prehensive data and understanding of the properties and features have been collected and evaluated which will be summarized in this article. Since the early developments of the P M HIP technology it has been observed that PM HIP alloys generally exhibit higher yield streng ths compared to their conventional counterparts, a feature that applies well for 316L. In this article this is demonstrated, both by using the Hall-Petch relationship as well as Picker ing ́s and Irvine ́s empirically derived relationship between composition and grain size for austenitic stainless steels. Furthermore, a mechanism generating the increased yield strength i n PM HIP 316L vs conventionally manufactured 316L will be proposed. Results also sh ow t at low oxygen contents itself is not a guarantee for good or increased performance in fo rm of mechanical properties, but that there are other features that is of similar or perhaps ev en higher importance in order to achieve good properties. The results of this article includ e microstructural properties derived from EBSD measurements as well as tensile and impact pro perties in a wide range of test temperatures of PM HIP 316L from several powder bat ches manufactured at different locations and processed with various HIP and heat t r ment procedures. Finally, some results regarding creep properties of PM HIP 316L is presen ted. Introduction Austenitic stainless steel 316L is one of the most c mmonly known and used stainless steel grades and the performance and properties of this a lloy in different product forms is well known. Powder Metallurgical manufacturing via Gas A tomization and Hot Isostatic Pressing is a manufacturing technology known to generate iso tropic microstructures, high cleanliness and often improved mechanical properties. In light of he recent ASME code case approval for PM HIP 316L [1], the properties of this alloy v ia this manufacturing process has become of increasing interest [2-4]. This article will giv e an overview of the properties of PM HIP 316L/316LN, how properties can be affected by varyi ng manufacturing process parameters and compare how they differ from the conventionally manufactured counterparts. Microstructure One of the large benefits with PM HIP manufacturing s that the microstructures of the manufactured components are homogeneous, isotropic and have high cleanliness. All these features apply also for PM HIP 316L/316LN and trans l tes into excellent ultrasonic inspectability [4]. Regarding cleanliness, the clea r majority of the non-metallic inclusions found in PM HIP 316L/316LN are well below 2.8 μm in size and are predominately constituted by oxides [2,3]. The oxides can origina te either from the melt which are later trapped within the powder particles (bulk oxides) o r fr m the surface oxide layer and oxide