440C Bearing Steel


440C VAR Stainless Bearing Steel, Aircraft Bearings VAR AMS 5618 better than 52100 / worse than XD15NW 250°F (120°C) -
440C Air-Melt Stainless Bearing Steel, Aircraft Bearings Air-Melt only AMS 5880/ AMS 5630 Better than 52100 / Worse than XD15NW 250°F (120°C) -

Stock Size Range

  • AMS 5618 VAR: 0.375"ø – 3.750"ø
  • AMS 5630/ AMS 5880 Air-Melt: 0.250"ø – 6.000"ø

Chemical Analysis

Carbon 0.95 - 1.20 Manganese 1.00 max
Chromium 16.00 – 18.00 Molybdenum 0.40 – 0.65
Silicon 1.00 max Copper AMS 5630/ AMS 5618 0.50 max, AMS 5880 0.75 max
Nickel 0.75 max Phosphorus AMS 5630/ AMS 5880: 0.040 max, AMS 5618 0.020 max
Sulfur 0.030 max

440C Weakness: Poor Corrosion Resistance.... Solution: XD15NW

440C (X105CrMo17)


More about XD15NW

- Full corrosion resistance: will withstand salt and water exposure

- Improvement over 440C: has shown to extend life over 440C many times

- Perfect for aerospace, food processing, paper mills, and any industrial use that requires less downtime or critical applications

- Boeing BMS 7-357 Certified for aircraft applications

- Ready to ship, today in diameters from .112"ø to 8.000"ø

XD15NW is a martensitic stainless steel primarily used for bearings and ballscrews. This grade was developed for high stress applications where high hardness, fatigue resistance and corrosion resistance are paramount. This is one of the few bearing steels on the market with a minimum hardness of 58HRC, with usage up to 500 degrees Celsius.


Aspect of the surface after 96 h salt spray (NaCl) exposure For both grades, heat treatment cycle: 1050 °C Oil/ -75 °C/ 180 °C

(Source: Aubert & Duval Brochure)

The most significant advantage to XD15nw is its high resistance towards corrosion. This plays a significant advantage for uses where bearing maintenance is costly; such as production lines or food processing.

  • Significantly better corrosion resistance relative to 440C (X105CrMo17)
  • HRC of at least 58 after tempering at low (around 180°C) and high (500°C) temperatures
  • Low residual austenite after heat treatment in order to ensure a high dimensional stability of the parts.
  • Heat treatment is relatively simple, utilizing standard equipment.

XD15nw: Grease free applications

When used with ceramic balls, XD15nw can even offer a total grease free applications. This combination is ideal for food processing and other industrial uses where a clean application is required. The XD15nw and ceramic bearing creates the ultimate in high performance bearings that will last the distance.

XD15NW Stocking Sizes

  • 0.112"ø to 8.000"ø (2.8 mm ø – 203.2 mm ø)
  • Stock Summary       (115 KB)  

XD15NW Chemical composition

  C Si Mn Cr Mo V N Ni
min. 0.37 - - 15.00 1.50 0.20 0.16 -
max. 0.45 0.60 0.60 16.5 1.90 0.40 0.25 0.30


XD15NW Specifications

X40CrMoVN16-2 UNS: S42025 Euro Number: 1.4123 SAE: AMS 5925 Boeing: BMS 7-357 Download Brochure: XD15NW LITERATURE


more information on XD-15nw