AISI 8620 Steel Shaft - Carburized & Heat Treated Yield & Fatigue Strength?

AISI 8620 Steel Shaft - Carburized & Heat Treated Yield & Fatigue Strength?
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Posted by: jdutton ^®

10/16/2009, 14:06:24

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I am designing a shaft and am working on the carburzation & heat treament process to be called out. To get an idea for size, the shaft is about 2.5" in diameter and 16" long. It will experience cyclic stresses of +/- roughly 200Mpa at 27Hz.

I am currently specifing the following treament:

3. HEAT TREAT: GAS CARBORIZE AT 900° C MAX. OIL QUENCH FROM
830/850° C. TEMPER AT 165° C MIN. DEEP FREEZING NOT PERMITTED.

4. CASE DEPTH: 0.55-0.68 TOTAL.

5. MICROSTRUCTURE: DEPTH OF CLEAR MARTENSITE-0.20 MIN. RETAINED AUSTENITE
20-65 PERCENT (TARGET 30). RETAINED AUSTENITE TO BE DETERMINED BY X-RAY DEFRACTION
METHOD AFTER TEMPER. THE MICROSTRUCTURE MUST BE FREE OF DETRIMENTAL CONSTITUTIENTS
LIKE CARBIDES (MASSIVE NETWORK), MICROCRACKS, FREE FERRITE ETC.

Does anyone have any leads to sources for yield and fatigue strength for a similar carburization/heat treament? My callout for case depth, temperatures, etc can change if I can find information on yield and fatigue strength. I will likely send out samples for testing to verify final yield strength, but I am looking for any info now as to final yield and fatigue strengths for gas carburized and tempered 8620 steel.

Thanks,
Justin

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