Thermochemical post-processing of additively manufactured austenitic stainless steel

Thermal stability of hierarchical microstructural features in additively manufactured stainless steel

“…All pole figures show a tetrad symmetry reflecting the 90° rotation between line scans in adjacent islands. This is analogous to previous research, where a 67° rotation between consecutive layers was reflected in the crystallographic texture [ 21 ]. In Fig.…”

“…The specimens were heat treated in a Netzsch STA449 F 3 thermobalance, where heating and cooling rates are accurately controlled. A protective atmosphere of argon was applied during the treatments and all measurements and analyses were conducted in the bulk of the specimen (∼1 mm from the surface), so the influence of surface reactions, as for example N 2 evaporation, can be excluded [ 21 ]. A heating rate of 20 K/min was applied until reaching 50 K below the setpoint temperature, from where the heating rate was reduced to 5 K/min to avoid temperature overshoot.…”

Additive Manufacturing Post-Processing Treatments, a Review with Emphasis on Mechanical Characteristics

“…Typically, depending on the reactivity of the metallic powders employed, the L-PBF process is performed in a closed chamber that is filled with an inert atmosphere, such as argon or nitrogen. The principal motivation for applying post-treatments to L-PBF parts are presented as follows and the primary factors behind the implementation of post-processing techniques on L-PBF parts lies in the pursuit of enhanced material properties and improved functional performance of the fabricated components: Residual stress [ 2 , 3 ]; Microstructure high porosity [ 4 , 5 ]; Microstructure instability [ 5 , 6 , 7 , 8 ]; Homogenization, microstructural refinement, and martensite-to-austenite reversion [ 9 ]; Parts distortion [ 6 ]; Heterogeneous microstructure [ 10 ]; Coarse plate martensite with uneven distribution [ 11 ]; Anisotropic microstructures [ 12 ]; Low material density [ 13 ]; Martensite matrix with trace amount of austenite phase [ 14 , 15 ]; Enhance superelasticity of NiTi structures [ 16 , 17 , 18 ]; Stress-induced cracks and residual porosity [ 19 ]; Intermetallic precipitates [ 20 ]; Internal defects, such as entrapped-gas-pores or lack-of-fusion [ 21 ]; High nitrogen content [ 22 ]; Porosity, grain morphology and precipitates [ 23 , 24 ]. …”

“…The effects of different thermochemical post-processing such as high temperature solution nitriding (HTSN) and low temperature nitrocarburizing (LTNC) on the microstructure and properties of additively manufactured 316L austenitic stainless steel were investigated in [ 22 ]. For transversally built specimens, the HTSN and also the HTSN + LTNC treatments resulted in decreasing the YS by 45%, the UTS by 14%, and the elasticity modulus by 5%… 6%.…”

“… The distribution of improvement efficiency index in different reference papers [ 3 , 4 , 7 , 8 , 20 , 22 , 26 , 31 , 32 , 33 , 34 , 38 , 41 , 43 , 47 , 48 , 50 , 52 , 53 , 54 , 56 , 67 , 71 , 82 , 84 , 90 , 96 , 98 , 99 , 102 ]. …”