904L stainless steel powder for laser cladding
904L stainless steel, as an ultra-low-carbon and highly alloyed austenitic stainless steel, is renowned worldwide for its outstanding corrosion resistance.
When this material is applied in powder form to laser cladding technology, its application field is further enhanced and expanded. This article will systematically analyze the technical characteristics of 904L stainless steel powder from the perspective of materials science and its application field of laser cladding.
Chemical composition (wt.%)
Ingredient
Chromium of 904L alloy will form a dense Cr₂O₃ passivation film on the material surface, which is the first line of defense against corrosive oxidizing media;
Nickel of 904L can stabilize the austenitic phase structure, ensuring the material’s phase stability in various corrosive environments;
4-5% Molybdenum element will significantly enhance the material’s resistance to pitting and crevice corrosion in chloride-containing environments. The equivalent value of pitting resistance can reach above 33.
1-2% Copper can enhance corrosion resistance to reducing media, especially sulfuric acid;
Ultra-low carbon content will effectively prevent the precipitation of chromium carbide in the sensitization zone, and prevent intergranular corrosion;
Powder production process of 904L:
Modern industries mainly use the gas atomization technology to prepare 904L stainless steel powder. This process ensures the following key characteristics of the powder:
> High sphericality: Excellent fluidity, suitable for automatic powder feeding systems
> Low oxygen content: Usually kept below 0.1%, to avoid metallurgical defects
> Narrow particle size distribution: A particle size range of 15-53 micrometers or 45-105 micrometers takes into account both deposition efficiency and surface quality (customized particle size is also available)
> High chemical homogeneity: The component stability between batches reaches ±0.5%
- Mechanical and Thermal Properties
| القيمة النموذجية | Remark | |
| قوة الشد | ≥490MPa | Room temperature |
| Yield strength (Rp0.2) | ≥220MPa | Room temperature |
| الاستطالة | ≥35% | Excellent plasticity, easy to process |
| الكثافة | 8.0 جم/سم³ | A little higher than 316L |
| Working temperature | long-term≤250°C short-term≤400°C |
Material behavior in laser cladding:
During the laser cladding process, the 904L powder undergoes a thermal cycle of rapid heating – melting – solidification:
> Melt pool temperature gradient: Cooling rate as high as 10⁵ – 10⁶ K/s.
> Microstructure evolution: Formation of fine spheroidal crystals and dendritic crystal structures.
> Element distribution characteristics: Due to rapid solidification, the degree of alloy element segregation has been significantly reduced.
> Phase transformation behavior: Maintains a single-phase austenite structure without the formation of harmful intermetallic phases.
Performance advantage of 904L after laser cladding:
904L stainless steel laser cladding layer has the following advantages compared to traditional manufacturing methods:
> Maintenance of corrosion resistance: rapid solidification process prevents the formation of harmful phases, thus maintaining the corrosion resistance of the base material.
> Excellent adhesion to the substrate: a metallurgical bonding can be achieved, with the bonding strength reaching over 400 MPa.
> Geometric degrees of freedom: Capable of achieving uniform coating on complex surfaces, with thickness adjustable within the range of 0.5 – 3 mm.
> Heat affected zone control: A narrow heat affected zone (typically less than 1 mm) reduces the impact on the performance of the base material.
Industrial application examples:
1. The petrochemical industry sector
The tube sheet of the heat exchanger in the sulfuric acid recovery unit of a certain oil refinery was laser cladded with 904L material:
> Corrosion resistance: In an environment of 80℃ and 50% sulfuric acid, the annual corrosion rate has decreased from 1.2 mm to below 0.1 mm.
> Service life: Extended from 18 months to over 5 years;
2. Marine engineering applications
Repair of the valve seat sealing surface of the seawater desalination unit on the offshore platform can maintain zero leakage in seawater with a chloride ion concentration of 3.5% to pass 6,000 cycles of opening and closing tests, the sealing performance remained intact.
Other Stainless steel alloy powder:
316L, 304L, 17-4PH, 15-5PH, 13-8PH, 410L, 420, 430L, SS465, 2205, 2507, F55, 904L, 309L, 310S, 321, 1.4091, 1.4501, 1.4957, 1.4542, 1.4462, 1.4410, 3.33
