Mehanical Properties of Electron Beam Welded Joints in Thick Gage CA6NM Stainless Steel

Gholipour

et al. 2021

JMMP

Self Cite

Hybrid manufacturing is often used to describe a combination of additive and subtractive processes in the same build envelope. In this research study, hybrid manufacturing of 18Ni-300 maraging steel was investigated using a Matsuura LUMEX Avance-25 system that integrates metal additive manufacturing using laser powder bed fusion (LPBF) processing with high-speed machining. A series of benchmarking coupons were additively printed at four different power levels (160 W, 240 W, 320 W, 380 W) and with the integration of sequential machining passes after every 10 deposited layers, as well as final finishing of selected surfaces. Using non-contact three-dimensional laser scanning, inspection of the final geometry of the 18Ni-300 maraging steel coupons against the computer-aided design (CAD) model indicated the good capability of the Matsuura LUMEX Avance-25 system for net-shape manufacturing. Linear and areal roughness measurements of the surfaces showed average Ra/Sa values of 8.02–14.64 µm for the as-printed walls versus 0.32–0.80 µm for the machined walls/faces. Using Archimedes and helium (He) gas pycnometry methods, the part density was measured to be lowest for coupons produced at 160 W (relative density of 93.3–98.5%) relative to those at high power levels of 240 W to 380 W (relative density of 99.0–99.8%). This finding agreed well with the results of the porosity size distribution determined through X-ray micro-computed tomography (µCT). Evaluation of the static tensile properties indicated that the coupons manufactured at the lowest power of 160 W were ~30% lower in strength, 24% lower in stiffness, and more than 80% lower in ductility relative to higher power conditions (240 W to 380 W) due to the lower density at 160 W.

Section: Methodsmentioning

confidence: 99%

Evaluation of Maraging Steel Produced Using Hybrid Additive/Subtractive Manufacturing

Gholipour

et al. 2021

JMMP

Self Cite

“…Before welding, coupons-250 mm long, 80 mm wide, and 90 mm thick-were machined from normalized and tempered CA6NM. For each weld, two coupons with a square butt joint configuration and no intentional gap were tack welded, demagnetized, and fixed in a clamping fixture for butt welding (Figure 1(a)), as described in [10].…”

Section: Methodsmentioning

confidence: 99%

“…e recommended guideline for welding heavy sections (>12 mm thick) of 13% Cr-4% Ni martensitic stainless steel is to reduce the cooling rate during solidification by preheating from 100°C to 170°C [7,14,15]. To preheat the CA6NM inside the EBW chamber, an EBZHT [16] was developed and validated by the authors previously [7,10,15]. In this study, multiple EBZHT passes were conducted to achieve the required temperature range.…”

Section: Methodsmentioning

confidence: 99%

“…Vickers microhardness testing, according to [22] and detailed in [10], was performed using a Struers DuraScan machine with the ecos Workflow ™ software module to obtain two-dimensional maps of the hardness distribution using a load of 500 g, a dwell period of 15 s, and interval spacing of 2 mm.…”

Section: Methodsmentioning

confidence: 99%

“…To generate the essential performance data needed to validate turbine product design for manufacturing assembly with EBW, a multiyear collaboration was undertaken to evaluate the feasibility of the process to join heavy section turbine materials, such as CA6NM [7] and UNS S41500 [8]. e mechanical performance data generated for both materials indicated that the welds exhibited high strength and toughness [9,10] without PWHT. However, the residual stresses after EBW (∼600 MPa) CA6NM [11] were 110% of the YS of the alloy and greater than that recommended to prevent the initiation of unstable/premature failure.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Through‐Thickness Residual Stresses, Microstructure, and Mechanical Properties of Electron Beam‐Welded CA6NM Martensitic Stainless Steel after Postweld Heat Treatment

Advances in Materials Science and Engineering

Lévesque

et al. 2020

Self Cite

In this study, the integrity of electron beam- (EB-) welded CA6NM—a grade of 13% Cr-4% Ni martensitic stainless steel—was assessed through the entire joint thickness of 90 mm after postweld heat treatment (PWHT). The joints were characterized by examining the microstructure, residual stresses, global mechanical properties (static tensile, Charpy impact, and bend), and local properties (yield strength and strain at fracture) in the metallurgically modified regions of the EB welds. The applied PWHT tempered the “fresh” martensite present in the microstructure after welding, which reduced sufficiently the hardness (<280 HV) and residual stresses (<100 MPa) to meet the requirements for hydroelectric turbine assemblies. Also, the properties of the EB joints after PWHT passed the minimum acceptance criteria specified in ASME sections VIII and IX. Specifically, measurement of the global tensile properties indicated that the tensile strengths of the EB welds in the transverse and longitudinal directions were on the same order as that of the base metal (BM). Evaluation of the local tensile properties using a digital image correlation (DIC) methodology showed higher local yield strengths in the fusion zone (FZ) and heat-affected zone (HAZ) of 727 MPa and 740 MPa, respectively, relative to the BM value of 663 MPa. Also, the average impact energies for the FZ and HAZ were 63 J and 148 J, respectively, and attributed to the different failure mechanisms in the HAZ (dimples) versus the FZ (quasi-cleavage consisting of facets and dimples). This study shows that the application of PWHT plays an important role in improving the weld quality and performance of EB-welded CA6NM and provides the essential data for validating the design and manufacturing process for next-generation hydroelectric turbine products.

Distortion and residual stresses in electron beam-welded hydroelectric turbine materials

Lévesque

Science and Technology of Welding and Joining

et al. 2016

Heavy-section assembly of hydroelectric turbine runner materials using single-pass, autogenous EBW was demonstrated to penetrate a 90-mm-thick butt joint. The welding-induced distortions and residual stresses were characterised to understand the impact of the materials and process conditions (e.g. preheating and/or PWHT). Using 3D optical measurements, the angular distortions of EB-welded UNS S41500 and CA6NM steels were determined to be 0.13°and 0.38°, respectively. The longitudinal residual stresses, measured through the contour method, had a M-shaped distribution throughout the thickness with minimum (∼−500 MPa) compressive stresses in the FZ and maximum (∼600 MPa) tensile stresses in the HAZ. After PWHT, the tensile and compressive stresses reduced to ∼100 MPa.