Deep Cryogenic Treatment - Deep Nitriding Hardening of Nitrided Gears 

Xinfengli Liquid Nitrogen Deep Cryogenic Treatment Equipment: Pioneering Deep Nitriding Hardening Technology for Gears

Xinfengli, a leading domestic brand in liquid nitrogen deep cryogenic treatment equipment, specializes in manufacturing cryogenic chambers, low-temperature assembly tools, deep cryogenic treatment systems, and liquid nitrogen high-low temperature test chambers. With years of expertise in low-temperature and food machinery, Xinfengli’s equipment offers unparalleled advantages in rapid freezing across multiple industries.

1. Advancements in Deep Nitriding Hardening Technology
To enhance the load-bearing capacity and unlock the full potential of nitriding, deep nitriding hardening technology has been developed. Traditionally, nitriding layers were perceived as shallow ("eggshell-like"), but advancements in nitriding steel alloys and processes have enabled nitriding to rival carburizing in many applications, offering unique benefits.

Technical Breakthroughs:

Deep Nitriding Hardening: This approach combines deep nitriding with substrate hardening, increasing the nitriding layer depth from <0.4 mm to 0.6–1.0 mm. Subsurface hardness at 0.3–0.5 mm exceeds 500 HV with a gradual hardness gradient.
Specialized Alloys: Two aging-hardened steels—20CrNi3Mn2Al and 20Cr3MnMoV (Table 1)—were developed to meet stringent requirements: nitriding layer depth >0.6 mm, subsurface hardness >600 HV at 0.4 mm, and substrate hardness >400–450 HV (42–46 HRC).
Key Innovations:
(1) Aging-Hardened Steels
Replacing conventional quenched and tempered steels, aging-hardened steels eliminate oil quenching. Air-cooled solution treatment followed by nitriding and aging in a single process achieves surface hardness >900 HV and substrate hardness >400 HV (42 HRC), streamlining manufacturing.

Table 1: Chemical Composition of Experimental Steels (wt%)
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(2) Deep Nitriding Hardening Process
By integrating nitriding and aging mechanisms, variable-temperature nitriding accelerates nitrogen diffusion. Ion nitriding leverages ion bombardment and cathode sputtering to enhance surface activation and defect density, boosting nitriding efficiency.

Performance Comparison:

20CrNi3Mn2Al: 870°C × 3h air-cooled solution treatment + 520–540°C × 80h ion nitriding.
38CrMoAl: 520–530°C × 50h ion nitriding.
20CrMnTi: 930°C carburizing + 850°C oil quenching.
Results show 20CrNi3Mn2Al achieves superior surface hardness, subsurface strengthening, and substrate hardness comparable to carburized steel (Figure X).

2. Gear Stress Analysis
Gears operate under complex contact and bending fatigue stresses. Subsurface shear stress often leads to nitriding layer spalling, making subsurface reinforcement critical for load-bearing capacity.

Research Findings:

Increased nitriding depth and substrate hardness correlate with higher contact and bending fatigue strength.
Deep ion nitriding of aging-hardened steels ensures robust performance under heavy loads.
Case Study:
20CrNi3Mn2Al after deep ion nitriding exhibits subsurface hardness >600 HV at 0.4 mm and substrate hardness >400 HV (42 HRC) (Table 2).

Table 2: Hardness and Layer Depth of 20CrNi3Mn2Al After Deep Ion Nitriding
[Insert Table 2 Data Here]

3. Application Prospects
Recommended Material: 20CrNi3Mn2Al steel for nitrided gears, leveraging deep nitriding hardening to meet demanding operational requirements.

Performance Metrics:

Conventional Steels (e.g., 42CrMo): Substrate hardness 28–38 HRC; subsurface hardness <400–500 HV at 0.4 mm.
20CrNi3Mn2Al: Surface hardness >900 HV; subsurface hardness 600–650 HV at 0.4 mm; substrate hardness 40–46 HRC; nitriding layer >0.7 mm.
Outlook:
Aging-hardened steels paired with deep nitriding hardening are poised to revolutionize heavy-duty gear manufacturing. Current nitrided gears (module ≤10 mm) could see modules exceed 10 mm, enabling high-performance gears for extreme loads.

Xinfengli’s liquid nitrogen deep cryogenic treatment equipment continues to drive innovation in material science, offering cutting-edge solutions for industrial applications.