• Stanadyne manufactures fuel pumps for the automotive industry• These components are made of austenitic, martensitic, and ferritic stainless steels• Stainless steels are used for their corrosion resistance and strength

• Stainless steels of interest are 304L, 431, 17-4PH, and 439• Dissimilar combinations being studied are 431/304L, 431/439, and 304L/17-4PH

• The components are currently autogenously laser welded• Occasional cracking of welds has led to unacceptable rejection rates of parts• Solid state cracking could be caused by brittle martensite• Solidification cracking could be caused by austenitic solidification

Background

Results & Discussion

Conclusions

Future Work

Motivation

Objectives & Approach

Acknowledgements

Alvin Kirksey, Chris Cotter, Tyler Davis

Dr. John Lippold, The Ohio State UniversityDave Palermo, Richard Pellini, Stanadyne

Weldability of Dissimilar Stainless Steels for Fuel Pump Applications

Find a proper dilution level between dissimilar stainless steelcombinations in question that is resistant to cracking in order toreduce fuel pump defect rate

• Use ThermoCalcTM to develop phase transformation diagrams foreach combination

• Create button melt samples for combinations of interest atvarying dilutions

• Receive laser welds from Stanadyne following a tapered jointgeometry which allows for dilutions at variable levels to beexamined

• Characterize microstructures in both button melts and laserwelds through hardness testing, metallography, and ferritemeasurement (Magne-Gauge)

• Utilize ThermoCalcTM, button melt, and laser weld results toconstruct a constitution diagram similar to the Schaefflerdiagram that predicts phases present

• Test additional dilution amounts and material combinations• Test additional laser welds to see if they are comparable to

button melts• Utilize laser weld joint geometry on 431/304L to determine at

which dilutions cracks occur

• The solidification behavior of all combinations consisted of either ferrite (F) or ferrite-austenite (FA) solidification mode

• Actual laser welded 17-4PH/304L samples made over the full range of dilution compared extremely well with button melts

• A revised Schaeffler diagram is proposed that shows an expansion of the A+F region and a truncation of the A+M+F region. None of button melt compositions that were produced exhibited a three phase microstructure

• Cracking in 17-4PH/304L laser welds favored dilutions exceeding ~60% 17-4PH.

100% 17-4PH 75%/25% 50%/50% 25%/75% 100% 304L

352 Vickers>24 FN

327 Vickers>24 FN

160 Vickers8 FN

156 Vickers7 FN

172 Vickers3 FN

M + F → M + F → F + A → F + A → F + A

17-4PH/304L Button Melt Samples

431/304L Button Melt Samples100% 431 75%/25% 50%/50% 25%/75% 100% 304L

405 Vickers>24 FN

434 Vickers>24 FN

215 Vickers15 FN

191 Vickers11 FN

172 Vickers3 FN

M + F → M + F → F + A → F + A → F + A

431/439 Button Melt Samples100% 431 75%/25% 50%/50% 25%/75% 100% 304L

405 Vickers>24 FN

331 Vickers>24 FN

217 Vickers>24 FN

172 Vickers>24 FN

163 Vickers>24 FN

M + F → M + F → M + F → F → F

Laser weld joint geometry performed on 17-4PH/304L

Button Melt Phases on Schaeffler Diagram New Proposed Schaeffler Diagram

The team would like to thank Dr. John Lippold for his guidance and expertise on procedures and evaluation of results. Thank you to Dave Palermo and Richard Pellini of Stanadyne in providing assistance, materials, welded samples, and the opportunity to work on this project. Thank you to graduate students who gave hands on assistance in the metallography lab. Thank you to Dr. Adam Hope of ThermoCalcTM for assistance in calculations.

Large drop in hardness for both button melts and laser welds between 75% and 50% 17-4PH. Cracks occurred in laser welds from 60%-100% 17-4PH