Zhuojin Pipe Fitting Co., LtdProcess Parameter Study for GTAW Overlay Welding 2Cr13 on 38CrMoAl
Literature Overview
This paper by Zhao Jiaming, Yue Fengli, Chen Zhuojun, and Chen Bin, published in the Journal of Shenyang Ligong University in 2020, investigates the gas tungsten arc welding (GTAW) overlay of 2Cr13 stainless steel onto 38CrMoAl alloy steel to improve the wear resistance of automotive engine crankshafts. The authors systematically examined the effects of welding current and argon gas pressure on the overlay layer's hardness, wear performance, and microstructural quality.
Core Technical Content
The selection of 2Cr13 as the overlay material is driven by its excellent wear resistance and moderate corrosion resistance properties, making it suitable for the tribological demands of crankshaft journals. The base material 38CrMoAl is a high-strength alloy steel commonly used in crankshaft manufacturing due to its favorable combination of strength, fatigue resistance, and machinability. The metallurgical compatibility between these two materials is a key concern, as the significant difference in alloy composition between the base and overlay creates challenges in achieving sound fusion without cracking or excessive hardness gradients.
The use of GTAW for this application is appropriate because it provides precise control over heat input, which is essential when welding thin overlay layers on high-strength alloy steels. The WSE-350 welding machine was used with 2Cr13 welding electrodes, and the study varied welding current from 110 to 150 A and argon gas pressure from 5 to 10 MPa.
Process Parameters and Performance Results
| Parameter Combination | Transition Layer Thickness | Hardness (Hv) | Wear Loss (mg) | Wear Rate (mg/min) | Defects |
|---|---|---|---|---|---|
| 5 MPa, 130 A | 0.008 mm | 3745.4 | 15.6 | 0.052 | None |
| 10 MPa, 130 A | 0.006 mm | 3651.4 | 23.3 | 0.078 | Porosity, concavity |
The results clearly demonstrate that the lower argon gas pressure condition (5 MPa) produced superior performance across all measured parameters. The overlay layer at 5 MPa exhibited higher hardness, lower wear loss, and a cleaner microstructure without porosity or concavity defects. The higher gas pressure at 10 MPa, counterintuitively, produced a thinner transition layer but with more welding defects and inferior wear performance.
Microstructural Analysis and Defect Evaluation
The microstructural examination using scanning electron microscopy revealed that the optimal condition (5 MPa, 130 A) produced a uniform overlay microstructure with good slag-metal interface bonding. The transition layer between the base metal and overlay was well-defined and free of defects. At the higher gas pressure condition, porosity and concavity defects were observed, which would compromise the structural integrity and fatigue performance of the overlay in service.
The wear testing was conducted using an MM-200 wear tester with a load of 900 N, rotational speed of 200 r/min, and wear duration of 300 min. These conditions simulate the tribological environment experienced by crankshaft journals during engine operation, providing a realistic assessment of the overlay's service performance.
Engineering Practice Integration
The practical significance of this research lies in its direct application to automotive crankshaft manufacturing. Crankshafts are critical engine components that experience high cyclic loading, friction, and impact during operation. The overlay of a wear-resistant stainless steel layer on the journal surfaces can significantly extend crankshaft service life and reduce maintenance costs.
The finding that lower argon pressure produces better results is an important process insight. In GTAW overlay welding, the shielding gas pressure affects the arc stability, weld pool convection, and slag behavior. Higher gas pressure may increase turbulence in the shielding gas flow, which can entrain slag inclusions or disrupt the solidification pattern, leading to porosity and surface irregularities.
The welding current of 130 A represents an optimal balance between penetration depth and heat input. Lower currents may not achieve sufficient fusion with the base material, while higher currents could cause excessive dilution or thermal distortion of the thin crankshaft journal geometry.
Key Reflections and Study Insights
This study exemplifies the systematic approach required for developing overlay welding processes for specific applications. The parameter matrix approach, where multiple variables are varied and their effects are quantified through standardized testing, provides a rigorous foundation for process optimization. The clear correlation between welding parameters, microstructure, and performance metrics is essential for establishing reliable welding procedure specifications.
The defect analysis is particularly instructive. The presence of porosity at higher gas pressure highlights the importance of understanding not just the macroscopic performance but also the microscopic quality of the overlay. In structural applications such as crankshafts, even small porosity defects can act as fatigue initiation sites, leading to premature failure under cyclic loading.
The transition layer thickness is another critical parameter that affects overlay performance. A well-controlled transition layer ensures gradual compositional and microstructural changes from base to overlay, minimizing stress concentrations at the interface. The results show that the optimal process condition produces a slightly thicker but more uniform transition layer, which likely contributes to better adhesion and lower residual stress.
This research provides valuable guidance for engineers developing GTAW overlay processes for high-strength alloy steel components in automotive and powertrain applications, demonstrating that careful parameter selection and microstructural quality control are essential for achieving reliable performance.