Comparison of Mechanical, Metallurgical Properties of 17-4PH Stainless Steel between Direct Metal Laser Sintering (DMLS) and Traditional Manufacturing Methods

The purpose of this research was to analyze and compare the mechanical properties of parts made using both Direct Metal Laser Sintering (DMLS) and traditional manufacturing methods like casting or forging. Previous research in DMLS was conducted using various materials, but there has been very little done for 17-4PH stainless steel. All the samples used for testing were conducted using the EOSINT ® M 270 metal sintering system made by EOS GmbH. The samples produced were tested under various post-processing conditions including solution treatment and age hardening. Metallurgical testing was also conducted in order to determine the effects of sintering with regards to phase formation during heat treatment. Tensile tests revealed that parts straight from the machine corresponded with values published by EOS GmbH, but results from age hardening were much lower than wrought components aged to the H 900 condition. When cross checking the results with hardness and microstructure, it was found that hardness vastly decreased during solutionizing and only increased marginally during aging. The microstructure was, there was also vastly different, little evidence of martensite was present in the solution treated condition, and the aged condition showed no transformation to tempered martensite. This lack of transformation points to inconsistences in either the DMLS process or from furnace conditions during heat treatment. 17-4PH stainless steel may be inferior in the precipitation hardened state, but produces comparable properties straight from the machine.