Characterization of Direct Metal Laser Sintered Alloy 718 in the As-Fabricated and Heat Treated Condition

Abstract

Additive manufacturing (AM) processes have been shifting from primarily prototyping products to the production of fully functional end parts and components. An understanding of the material characteristics necessitates an evaluation of the mechanical and corrosion behavior in order to determine and quantify the limitations of AM processes.

This paper focuses on characterizing Alloy 718 produced via the Direct Metal Laser Sintering (DMLS) process in the as-fabricated and heat treated condition. The printed Alloy 718 material was produced on a single plate comprised of rectangular, cylindrical and round shapes of varying section thickness that were subjected to evaluation that included chemistry, microstructural, mechanical, fatigue and corrosion testing. Heat treated sections were solution annealed and precipitation hardened in accordance with API 6ACRA.

INTRODUCTION

The precipitation hardened nickel based alloys are widely utilized for downhole applications such as drilling and completion equipment. Additive manufacturing, or three-dimensional (3-D) printing, has received a great deal of attention in recent years. Additive manufacturing is a suite of emerging technologies that fabricates three-dimensional objects directly from digital models through an additive process, typically by depositing and ”curing or solidifying in place” successive layers of polymers, ceramics, or metallics. Unlike traditional manufacturing processes involving subtraction (e.g., cutting and shearing) and forming (e.g., stamping, bending, and molding), additive manufacturing joins materials together to build products. Additive manufacturing technology is shaping the future of product development and manufacturing in small complex geometry components and specialized applications.

Additive manufacturing was originally conceived as a way to make prototypes but has slowly transformed itself to the extent that it is increasingly being used to deliver final products. Recent improvements include enhancements of the speed and performance of additive manufacturing machinery, an expanding range of input materials, and falling prices for both machinery and materials. The development of AM technology and the state-of-the-art has recently been accelerating because of improvements in laser and electron beam AM equipment using powder injection, powder bed or wire feed systems that has also benefited by advances in the build for additive manufacture software programs. The new design for manufacturing software programs in developments such as predictive modeling of residual stresses during the laser powder bed builds helps identify issues with a given design or build orientation to reduce/eliminate build failures.