GB/T 45867-2025 in English

Standard Development Background and Technological Evolution

GB/T 45867-2025, "Technical Specification for Integrated Forming of Cobalt-Based Alloys and Stainless Steel Dissimilar Metals for Additive Manufacturing," is China's first technical standard specifically for dissimilar metal additive manufacturing. This standard was developed based on the urgent demand for high-performance dissimilar metal structural components in China's nuclear power equipment, aerospace, and other fields, particularly given the significant technological maturity of directed energy deposition equipment.

Key Terms and Definitions

Dissimilar Metal Integrated Forming: Directed energy deposition technology is used to achieve the integrated forming of two dissimilar metal materials, cobalt-based alloys and stainless steel. This technology overcomes the limitations of traditional manufacturing methods in terms of material compatibility and structural complexity.

The standard specifies the combination of a laser energy source and powder raw materials, ensuring precise control of the forming process and predictable material properties.

Comparison of technical requirements of raw materials

Key Technical Points of the Process

6.2 Model Design Specifications

Model design must consider material thermal expansion coefficient differences (cobalt-based alloys: 14.0×10⁻⁶/°C, stainless steel: 16.0-18.0×10⁻⁶/°C). Thermal stress concentration should be avoided through rational structural design. A three-dimensional conformal distribution design allows for flexible adjustment of material distribution within space to meet the requirements of complex service conditions.

6.3 Process Parameter Optimization

Process parameter settings for the dissimilar metal interface area: laser power 2000-4000W, scan rate 5-15mm/s, and interlayer dwell time 10-30s. Process testing will be conducted to determine the optimal parameter combination to ensure interface fusion quality.

Quality Inspection System Construction

7.1 Inspection Item Matrix

The standard establishes a three-tiered inspection system: mandatory inspection items (√), optional inspection items (○), and exempt inspection items (-). The interface area between dissimilar metals is a key inspection area and requires comprehensive testing of chemical composition, metallographic structure, and mechanical properties.

7.2 Test Method Refinement

Metallographic inspection requires attention to structural changes within a 0.5mm range on both sides of the interface, including grain size and phase composition. For tensile testing, specimens should be prepared centered on the interface to test the strength properties of the bonding area.

Implementation Recommendations and Risk Control

Equipment Selection Recommendations

It is recommended to use a directed energy deposition equipment with a dual powder feeding system. The powder feeding accuracy should reach ±1%, and the laser positioning accuracy should reach ±0.05mm.

Process Validation Process

Process qualification testing is required before implementation, including: single-material process parameter optimization, interface transition zone process testing, and furnace specimen performance testing.

Quality Control Key Points

Focus on monitoring key indicators such as oxygen content in the interface area (≤0.06%), defect density (≤0.5%), and residual stress (≤70% of the material's yield strength).

Application Prospects and Technological Development Trends

The implementation of this standard will promote the large-scale application of dissimilar metal additive manufacturing technology in high-end equipment such as nuclear power main equipment and aircraft engines. Future technological development will focus on multi-material gradient composite manufacturing, online monitoring, and intelligent control.