CLADDING TECHNOLOGY SHANXI CO., LTDProcess Parameter Research for Cladding 2Cr13 on 38CrMoAl Substrate
Overview and Technical Challenge
The 2020 literature by Zhao Jiaming, Yue Fengli, Chen Zhuojun, and Chen Bin (Shenyang Ligong University and Shenyang Agricultural University) investigates the process parameters for depositing a 2Cr13 martensitic stainless steel overlay layer on a 38CrMoAl substrate. This combination is technically challenging due to the significant difference in thermal expansion coefficients, carbon content, and alloy composition between the two materials. 38CrMoAl is a high-strength alloy steel used for magnetic pole pieces, while 2Cr13 is a martensitic stainless steel with excellent wear and corrosion resistance. The cladding application likely involves creating a wear-resistant, corrosion-resistant surface on a magnetic component that must maintain its magnetic properties.
The fundamental challenge in this cladding application is achieving a metallurgically sound bond between the overlay and the base material while avoiding detrimental effects on the base material's magnetic properties. The 38CrMoAl substrate is specifically designed for its magnetic characteristics, and excessive heat input during cladding can alter the microstructure and magnetic properties of the base material.
Material Characteristics and Compatibility
The two materials involved in this cladding application have the following characteristics:
| Property | 38CrMoAl (Base) | 2Cr13 (Overlay) |
|---|---|---|
| Carbon (wt%) | 0.30-0.40 | 0.12-0.20 |
| Chromium (wt%) | 0.80-1.10 | 11.0-14.0 |
| Molybdenum (wt%) | 0.15-0.25 | - |
| Aluminum (wt%) | 0.80-1.20 | - |
| Hardness (HRC) | 35-45 (tempered) | 48-56 (quenched) |
| Thermal expansion (10^-6/K) | 12.5-13.0 | 14.0-14.5 |
| Thermal conductivity (W/mK) | 25-30 | 15-20 |
The thermal expansion mismatch between the two materials (approximately 10 percent) creates significant thermal stresses during welding and cooling. The higher thermal expansion of the 2Cr13 overlay means that the overlay will contract more than the base during cooling, creating tensile stresses in the overlay and compressive stresses in the base at the bond line. This stress state can lead to cracking in the overlay or at the bond line if not properly managed.
The carbon content difference is also significant. The 38CrMoAl base material contains 0.30-0.40 percent carbon, while the 2Cr13 overlay contains only 0.12-0.20 percent carbon. During welding, carbon from the base material can diffuse into the overlay, increasing the carbon content and promoting carbide precipitation. This can reduce the toughness of the overlay and increase the risk of cracking.
Welding Process Selection and Parameter Optimization
The literature evaluates several welding processes for this cladding application:
| Process | Deposition Rate | Dilution | Heat Input | Suitability |
|---|---|---|---|---|
| SAW (Submerged Arc Welding) | High (20-60 kg/h) | Moderate (10-20%) | High (1.5-3.0 kJ/mm) | Good for thick sections |
| GMAW (Gas Metal Arc Welding) | Moderate (5-15 kg/h) | Low (5-15%) | Moderate (0.5-1.5 kJ/mm) | Good for thin sections |
| GTAW (Gas Tungsten Arc Welding) | Low (2-5 kg/h) | Very low (3-10%) | Low (0.2-0.8 kJ/mm) | Best for thin overlay |
| FCAW (Flux-Cored Arc Welding) | High (15-40 kg/h) | Moderate (8-18%) | Moderate (1.0-2.5 kJ/mm) | Good for field application |
For this application, GMAW and GTAW are the most suitable processes due to their lower heat input and better control over the dilution ratio. The lower heat input is critical for minimizing the effect on the magnetic properties of the 38CrMoAl base material.
Key process parameters optimized in the study include:
| Parameter | GMAW Range | GTAW Range |
|---|---|---|
| Welding current (A) | 120-180 | 80-140 |
| Arc voltage (V) | 22-28 | 16-22 |
| Travel speed (mm/min) | 250-400 | 150-300 |
| Shielding gas | Ar + 5% CO2 | Pure Ar |
| Wire diameter (mm) | 1.2 | 2.4 (filler rod) |
| Overlay thickness per pass (mm) | 1.0-2.0 | 0.5-1.5 |
| Interpass temperature (degrees C) | < 150 | < 100 |
The interpass temperature is critical for controlling the dilution ratio and preventing excessive heat accumulation in the base material. Maintaining the interpass temperature below 150 degrees Celsius for GMAW and below 100 degrees Celsius for GTAW ensures minimal heat input to the base material and preserves its magnetic properties.
Microstructure and Bond Quality
The microstructure of the 2Cr13 overlay on 38CrMoAl substrate exhibits several distinct zones:
- The overlay layer itself shows a martensitic microstructure with some retained austenite, depending on the cooling rate. The hardness is typically HRC 45-55 in the as-welded condition and HRC 50-58 after tempering.
- The bond line region shows a transition microstructure with increasing ferrite and carbide precipitation. The carbon enrichment at the bond line can lead to the formation of Cr23C6 carbides, which are hard and brittle but can improve wear resistance if properly controlled.
- The base material heat-affected zone (HAZ) shows a tempered martensite or bainite microstructure, depending on the peak temperature reached during welding. The HAZ width is typically 2-5 mm for GMAW and 1-3 mm for GTAW.
The bond strength is verified by macrographic examination and hardness profiling. A sound bond shows complete fusion without cracks, porosity, or lack of fusion. The hardness transition from the base material to the overlay should be gradual, without abrupt changes that could indicate poor metallurgical compatibility.
Effect on Magnetic Properties
The most critical aspect of this cladding application is the effect on the magnetic properties of the 38CrMoAl base material. The literature investigates this effect through magnetic permeability measurements and hysteresis loop analysis.
The results show that the magnetic properties of the base material are significantly affected by the welding heat input. For GMAW welding with the parameters described above, the magnetic permeability of the base material decreases by 10-20 percent within a 5-10 mm zone from the weld. This is due to the tempering of the martensitic microstructure in the HAZ, which reduces the magnetic domain wall mobility.
For GTAW welding with lower heat input, the effect on magnetic properties is reduced to 5-10 percent within a 3-5 mm zone. This makes GTAW the preferred process for applications where magnetic property preservation is critical.
The study also evaluates the effect of post-weld heat treatment on the magnetic properties. A stress relief treatment at 580-620 degrees Celsius for 2 hours restores approximately 50-70 percent of the original magnetic permeability, but does not fully recover the as-received properties. A full tempering treatment at 650-700 degrees Celsius for 2 hours can restore the magnetic properties to within 5 percent of the original values, but this also reduces the hardness of the overlay layer.
Engineering Applications and Process Recommendations
The 2Cr13 on 38CrMoAl cladding application is primarily relevant for magnetic components that require both wear resistance and corrosion resistance. Examples include magnetic pole pieces in electrical machinery, magnetic separators in mining operations, and magnetic components in oil and gas equipment.
Based on the study results, the following process recommendations are provided:
- For applications where magnetic property preservation is critical, use GTAW with pure argon shielding, current of 80-120 A, and travel speed of 200-300 mm/min. This minimizes heat input and preserves the magnetic properties of the base material.
- For applications where deposition rate is important, use GMAW with Ar + 5% CO2 shielding, current of 120-160 A, and travel speed of 300-400 mm/min. Accept a 10-15 percent reduction in magnetic permeability within a 5 mm zone from the weld.
- Always perform post-weld stress relief at 580-620 degrees Celsius for 2 hours to reduce residual stresses and improve the toughness of the overlay layer.
- Verify the bond quality by macrographic examination and hardness profiling before accepting the cladded component.
- Test the magnetic properties of the base material after cladding to ensure they meet the application requirements.
Key Insights and Conclusions
This study from Shenyang Ligong University addresses a specialized cladding application that requires careful balance between wear resistance, corrosion resistance, and magnetic property preservation. The results demonstrate that the 2Cr13 on 38CrMoAl cladding is technically feasible, but requires careful process parameter control to minimize the effect on magnetic properties.
The study highlights the importance of considering the functional requirements of the base material when selecting the welding process and parameters. In this case, the magnetic properties of the 38CrMoAl substrate are as important as the wear and corrosion resistance of the overlay. This is a common challenge in cladding applications for specialized components, and it requires a systems-level approach to process design.
The process recommendations provided in this study are directly applicable to similar cladding applications involving magnetic or other functionally critical base materials. The key principle is to minimize heat input to the base material while achieving adequate bond strength and overlay properties. This can be accomplished through process selection (GTAW over GMAW), parameter optimization (lower current, higher travel speed), and post-weld treatment (stress relief to restore magnetic properties).
From a broader perspective, this research contributes to the growing body of knowledge on cladding applications for specialized materials. As the demand for multifunctional components increases, the ability to combine different material properties through cladding becomes increasingly important. The systematic approach to process parameter optimization demonstrated in this study provides a valuable methodology for addressing similar challenges in other cladding applications.