On the toughness scatter in low alloy C-Mn steel samples fabricated using wire arc additive manufacturing

Abstract Low alloy carbon manganese (C-Mn) steel builds were fabricated using a wire based additive manufacturing system developed at Oak Ridge National Laboratory. Specimens were fabricated in the X,Y and Z direction and detailed mechanical testing was performed. The mechanical testing results showed a significant scatter in tensile ductility and significant variation in Charpy toughness. Further detailed microstructure characterization showed significant microstructural heterogeneity in builds fabricated in each direction. The scatter in mechanical properties was then rationalized based on the microstructural observations and the underlying changes in the local heat transfer conditions. The results indicate that when fabricating parts using C-Mn low alloy steel welds the process parameters and tool path should be chosen such that the cooling rate from 800 °C to 500 °C is greater than 30 s to avoid formation of martensite austenite (MA) phases, which leads to toughness reductions.

[1]  B. Gretoft,et al.  A model for the development of microstructure in low-alloy steel (Fe-Mn-Si-C) weld deposits , 1985 .

[2]  H. K. D. H. Bhadeshia,et al.  Transition from bainite to acicular ferrite in reheated Fe–Cr–C weld deposits , 1990 .

[3]  H. K. D. H. Bhadeshia,et al.  Mechanism of the Transition from Bainite to Acicular Ferrite , 1991 .

[4]  Amit K. Ghosh.  Tensile instability and necking in materials with strain hardening and strain-rate hardening , 1977 .

[5]  J. F. Knott,et al.  Effect of reheating on microstructure and toughness of C–Mn weld metal , 1983 .

[6]  William E. Frazier,et al.  Metal Additive Manufacturing: A Review , 2014, Journal of Materials Engineering and Performance.

[7]  C. Van Tyne,et al.  On the Formation of a Non-Traditional Pearlite Morphology , 2007 .

[8]  H. Bhadeshia,et al.  Diffusional formation of ferrite in iron and its alloys , 1987 .

[9]  B. Gretoft,et al.  Microstructure and Impact Toughness of C-Mn Weld Metals The formation of acicular ferrite in over half of the weld appears to be the key to improving impact toughness , 1990 .

[10]  S. Suresh Babu,et al.  Effect of microstructural heterogeneities on scatter of toughness in multi-pass weld metal of C–Mn steels , 2014 .

[11]  Sergio D. Felicelli,et al.  Residual stresses in LENS-deposited AISI 410 stainless steel plates , 2008 .

[12]  Lonnie J. Love,et al.  Additive manufacturing of materials: Opportunities and challenges , 2015 .

[13]  Paul A. Colegrove,et al.  Microstructure and residual stress improvement in wire and arc additively manufactured parts through high-pressure rolling , 2013 .

[14]  D. Matlock,et al.  Microstructural development in mild and low-alloy steel weld metals , 1986 .

[15]  P. Michaleris,et al.  Residual stress and distortion modeling of electron beam direct manufacturing Ti-6Al-4V , 2015 .

[16]  Julia King,et al.  Cleavage initiation in the intercritically reheated coarse-grained heat-affected zone: Part I. Fractographic evidence , 1994 .

[17]  Julia King,et al.  Effect of cooling rate on intercritically reheated microstructure and toughness in high strength low alloy steel , 1993 .

[18]  C. H. Cáceres.  On the effect of macroporosity on the tensile properties of the Al-7%Si-0.4%Mg casting alloy , 1995 .

[19]  Zengxi Pan,et al.  Wire-feed additive manufacturing of metal components: technologies, developments and future interests , 2015 .

[20]  S. Babu,et al.  The mechanism of acicular ferrite in weld deposits , 2004 .

[21]  R. Poprawe,et al.  Laser additive manufacturing of metallic components: materials, processes and mechanisms , 2012 .

[22]  C. H. Cáceres,et al.  Casting defects and the tensile properties of an AlSiMg alloy , 1996 .

[23]  Odd M. Akselsen,et al.  Structure–property relationships in intercritical heat affected zone of low-carbon microalloyed steels , 1987 .

[24]  E. Gibson,et al.  The divorced eutectoid transformation in steel , 1998 .

[25]  Choong Do Lee.  Effects of microporosity on tensile properties of A356 aluminum alloy , 2007 .

[26]  S. Babu,et al.  In pursuit of optimum welding system design for steels , 2011 .

[27]  D. Y. Lee,et al.  Microstructure and local brittle zone phenomena in high-strength low-alloy steel welds , 1991 .