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PRODUCT DATA of AISI 440C
MaterialAISI 440C
Product Datasheet440C
General InformationThis is a high carbon martensitic stainless steel with moderate corrosion resistance good strength and the ability to obtain and keep excellent hardness (Rc 60) and wear resistance. Ball bearings and races.

Data for hardened and stress relieved

PrecautionsCracking may occur on heating, cooling, pickling or after welding. This steel is particularly subject to decarburization because of their high carbon content. Use of protective, non-decarburizing atmospheres in heat treatments is recommended. This steel is subject to severe embrittlement by gaseous hydrogen
Chemical CompositionFe-17Cr-0.75Mo-1.2C
EXPERIENCE IN PRACTICE
Development StatusCommercial Product
Cost RangeLow
Equivalent Designations1.4125; X105CrMo17; Z100CD17
Space ExperienceGood
PHYSICAL PROPERTIES
Crystal StructureFace centered cubic (fcc)
Specific Gravity7.75
Magnetic PropertiesFerromagnetic
ELECTRICAL PROPERTIES
Electrical Volume Resistivity6e-7 ohm.m
THERMAL PROPERTIES
Thermal Expansion Coefficient10.2 μstrain/°C
Melting Range1370 to 1480 °C
Specific Heat0.46 J/g.K
RELEVANT PROPERTIES FOR USE IN SPACE COMMUNITY
General Corrosion StatusRequires specific corrosion protection
Atmospheric CorrosionThis alloy is not really stainless. Should be covered with oil or grease at all times
Stress Corrosion StatusLow Resistance to SCC: Table 3
Data Quality: Design Data
EMF vs SCE-0.2 V
Remark: Measured in 3.5% NaCl solution. Passive condition
Data Quality: Design Data
Bimetallic CorrosionCan be connected without any restriction to: Cr, Au, Ag, Gun-metal, P-bronzes, Sn-bronzes, Ti+alloys, Ni, Monel, Inconel, Ni/Mo alloys
Can be connected in a non-controlled environment to the above and Cd, austenitic cast iron, Cu, Brasses, Al-bronzes, Si-bronzes, Au, Pt, C, Rh, Sn-Pb alloys, Sn, Pb, 300 series stainless steels
Can be connected in a clean room environment to above and Al-Cu alloys
Needs specific measures: All others
Test:ECSS-Q-ST-70C Rev.1 Table 5.1
Data Quality: Design Data
MachinabilityThis alloy is difficult to machine. Machining is generally performed in the fully annealed condition for bar and forgings, and in the spheroidized condition for castings. The use of carbide or ceramic tools is recommended. Machinability rating of these alloys is about 40 percent of that of mild steel.
WeldingThis alloy is not commonly welded due to its tendency to air harden.
FLUID SYSTEMS COMPATIBILITY
Low Pressure Hydrogen (LOH2)Fails mechanical impact
High Pressure Hydrogen (HIH2)Fails mechanical impact
SPECIAL RECOMMENDATIONS
Special RecommendationsCracking may occur on heating, cooling, pickling or after welding. These steels are particularly subject to decarburization because of their high carbon content. Use of protective, on-decarburizing atmospheres in heat treatments is recommended.