Clutch retainer plate failure

Failure analysis of a clutch Retainer plate field Failure

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Type Of failure

Window failure

Damper spring popping out Materials info consultancy private limited

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Type Of failure ➢The clutch Retainer plate was found to have failed in the field . ➢Due to the failure the damper spring Popped out as the plate could not retain the same due to window failure ➢This resulted in clutch not working in the vehicle ➢Also abnormal sound was reported during the failure Materials info consultancy private limited

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Examination of Failure ➢ The Failed clutch was examined Visually. ➢ The retainer plate window was found broken and the piece had got dislodged. ➢ The damper spring was found coming out of the window ➢ The spring was found to have rubbing marks on its surface ➢ With careful examination Gouging marks were seen on drive plate window sides where damper spring was seated.

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Examination of Failure Drive plate

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Examination of Failure ➢ The damper spring is located in drive plate window and gets retained by retainer plate on both sides. ➢ The Drive plate window was found to have deep digging ( Gouging ) on both ends where damper spring was making contact . ➢ This was resulting in damper spring getting loosened and coming out and hitting the retainer plate ➢ This hitting action was resulting in failure of retainer plate window.

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Failure Investigation ➢ Material and manufacturing process for Retainer plate: ➢ Material : IS 513 ( SAE 1010) type D ➢ Manufacturing process: Blanking Heat treatment i.e Carbonitriding Zinc Phosphating

➢ Hardness and case depth were checked for the failed retainer plate and were found to conform to the specification with no manufacturing or material defects Materials info consultancy private limited

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Failure Investigation ➢ Material and manufacturing process for Drive plate: ➢ Material : IS 513 ( SAE 1010) type D ➢ Manufacturing process: Blanking Heat treatment i.e Carbonitriding Zinc Phosphating

➢ Hardness and case depth were checked for the failed drive plate The effective case depth was found low due to formation of intermediate Pearlitic phases in the case.

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Failure Investigation

Pearlite formation in case Materials info consultancy private limited

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Failure Investigation ➢ Chemistry was checked for the drive plate and the material was found to be Aluminum killed ➢ Material : IS 513 ( SAE 1010) type D. Aluminum : 0.023% ➢ Use of Aluminum as Deoxidation agent resulted in fine grain size ➢ The grain size was measured and found ASTM 8-9 ➢ The fine grain size resulted in poor hardenability of the steel resulting in formation of intermediate phase Pearlite.

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Corrective Action ➢ While localization, the raw material was developed as Silicon killed steel in place of Aluminum as deoxidation.

➢ Material : IS 513 ( SAE 1010) type D. ➢ The material was blanked and carbonitrided in seal quench furnace using LPG and endogas. ➢ The case depth was measured using effective case depth method by microhardness and also microstructure was analyzed.

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Corrective Action ➢ The grain size was found 6-7 ASTM. ➢ Both microstutcure in case as well as effective case depth values were found conforming to specification. ➢ Rockwell superficial hardness was measured on components for around 25 heat treated batches and case depth was correlated witth superficial hardness ➢ Ensuring the hardness resulted in attainment of specified case depth.

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Testing and confirmation ➢ The drive plates were assembled in clutch assembly and were evaluated for durability in fatigue rig for required number of cycles ➢ Few clutch assemblies were tested on vehicles and found to cover more than 1.5lac cycles compared to earlier failure cases where life was as low as 20000-30000 kms.

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