MIG Arc Additive Manufacturing of 2Cr13 Stainless Steel Thin-Walled Components

Literature Overview

This study by Jiangsu University researchers, supported by the National Natural Science Foundation of China and the Anhui Provincial Key Laboratory of Special Welding Technology, investigates the microstructure and mechanical properties of thin-walled components fabricated by MIG arc additive manufacturing (AM) using 2Cr13 (a martensitic stainless steel, equivalent to AISI 420). The work addresses a significant industrial need: rapid prototyping and low-volume production of complex stainless steel components with the economic advantages of wire-fed arc AM.

Core Technical Content

2Cr13 Material Characteristics and AM Challenges

2Cr13 is a 13% chromium martensitic stainless steel known for its excellent wear resistance and moderate corrosion resistance. Its composition (approximately 12–14% Cr, ≤1% C, 0.4–0.6% Mo) gives it a hardenable microstructure that can achieve 45–55 HRC in the heat-treated condition. However, several challenges arise when applying MIG arc AM to this material:

Challenge	Root Cause	Mitigation Strategy
High residual stress	Large thermal gradients between layers	Interpass temperature control, layer strategy optimization
Cracking susceptibility	High carbon content promotes martensitic transformation	Low heat input, preheating, interpass stress relief
Oxidation and porosity	Open arc process exposes molten pool	Adequate shielding gas coverage, wire composition control
Dimensional accuracy	Thermal distortion accumulation	Fixturing strategy, in-situ monitoring
Heterogeneous microstructure	Multi-pass thermal cycling effects	Post-build heat treatment, parameter uniformity

Microstructural Evolution in MIG AM

The as-built microstructure of MIG AM 2Cr13 components typically exhibits:

Coarse columnar martensite in the as-deposited condition due to rapid solidification rates (typically 10–100 °C/s)
Retained austenite content that varies with carbon equivalent and cooling rate
Carbide precipitation (M23C6, Cr7C3) at prior austenite grain boundaries
Layer-wise microstructural differences due to thermal history variations
Potential for lenticular martensite morphology in thicker sections

The thin-walled nature of the components adds another dimension of complexity. Thin walls (<3 mm) experience different thermal conditions than bulk components—the heat dissipation is more rapid, leading to higher cooling rates and potentially more martensitic transformation. However, the limited cross-section also means that residual stresses may be less constrained, potentially reducing the cracking tendency.

Mechanical Property Assessment

The mechanical properties of MIG AM 2Cr13 thin-walled components are expected to show:

Tensile strength: 600–800 MPa in as-built condition (lower than wrought due to retained austenite)
Hardness: 35–45 HRC in as-built condition
Elongation: 5–12% depending on retained austenite content
Fatigue properties: potentially anisotropic due to layer-wise deposition direction

The directional dependence of mechanical properties is a critical consideration for component design. Properties parallel to the build direction may differ significantly from those perpendicular to it due to the columnar grain structure.

Process Parameters and Quality Control

Parameter	Typical Value	Effect on Quality
Welding Current	150–250 A	Higher current → thicker layers, more retained austenite
Travel Speed	500–1500 mm/min	Lower speed → higher heat input, coarser microstructure
Wire Feed Speed	3–8 m/min	Must match travel speed for consistent bead geometry
Shielding Gas	Pure Ar or Ar + 2% CO2	CO2 addition increases penetration but may increase oxidation
Interpass Temperature	100–200 °C	Critical for crack prevention in martensitic stainless steels
Layer Thickness	1.5–3.0 mm	Thinner layers → better mechanical properties but longer build time

Quality assurance for MIG AM thin-walled components requires:

Visual inspection of each layer for lack of fusion and porosity
Ultrasonic testing for internal defects in thicker sections
Dimensional metrology to verify geometric accuracy within specified tolerances
Hardness mapping to identify microstructural heterogeneity
Mechanical testing of coupon specimens built with identical parameters as the component

Engineering Practice and Applications

MIG AM of 2Cr13 thin-walled components finds application in:

Wear-resistant liners and sleeves for mining and quarry equipment
Custom tooling and fixtures for manufacturing operations
Replacement parts for legacy equipment where conventional machining is impractical
Prototype development for new stainless steel component designs
Repair and remanufacturing of worn thin-walled components

The economic advantage of MIG AM over conventional methods is most pronounced for low-volume, high-complexity components. For thin-walled parts specifically, the ability to build walls of varying thickness within a single component offers design flexibility that is difficult to achieve through conventional manufacturing.

Study Insights and Reflections

This research addresses a practically important gap in the AM community—the application of wire-fed arc processes to martensitic stainless steels. The 2Cr13 material is widely used in wear-resistant applications, and the ability to rapidly fabricate complex geometries in this material opens new design possibilities. The key challenge remains managing the martensitic transformation and associated residual stresses. From a standards perspective, the qualification of MIG AM procedures for pressure-retaining applications would require demonstration of mechanical property consistency across multiple builds and orientations, which is currently an evolving area of standards development. The Jiangsu University team's multi-institutional collaboration with CAS Hefei Institutes suggests a strong commitment to advancing this technology from laboratory to industrial application.