Ti6Al4V ELI (Grade 23) Metal Powder Feedstock for Additive Manufacturing: the effects of storage conditions on interstitial pick up at ambient temperatures and shelf life.

Ti6Al4V ELI (Grade 23) is a popular metal additive feedstock for industries with highly customized and complex parts, specifically medical and aerospace industries. The ELI designation limits the amount of interstitials in the composition, creating materials with less likelihood of forming brittle phases during manufacturing, necessary for the safe use in critical part applications. It is widely believed that the oxide layer formed during atomization of the metal powder feedstock is the predominant source of oxygen and other interstitials, that at ambient conditions such as those encountered during storage and handling, no further pick-up of oxygen, nitrogen or hydrogen will occur. This study will quantify the ambient environment effects of storage, storage duration (shelf life) and handling on the Ti6Al4V ELI powder’s interstitial quantities, bulk behavior and structure over an extended period of time. Two typical locations inside an additive manufacturing site representing middling and extreme environmental exposure will house samples of two lots of powder with different manufacturing dates in four storage conditions: 1) closed (to be opened at six months), 2) closed (to be opened at twelve months), 3) opened, mixed, sieved, replaced in original containers and closed, and 4) opened, with modified “open”-to-environment lids. Powder from each location-condition combination will be sampled and characterized for size, morphology, powder microstructure, powder behavior and interstitial content at regular intervals throughout the course of the study. Printed material properties, using the studied powder will also be evaluated for microstructure, mechanical properties and interstitial content. This study will provide data for informed decision-making where supposition has largely lead critical application industries to adopt conservative approaches to powder handling and storage. This information could result in a wider adoption of T6Al4V ELI additive manufacturing if cost savings could be realized from adjusted, less conservative, but sufficient handling and storage protocols.