Experimental studies on key-hole plasma arc welding process parameters of AISI 304 HCu stainless steel tube joints

Abstract

AISI 304HCu is a super austenitic stainless steel with alloying elements adding its capacity to retain the ability to withstand mechanical and corrosion resistance at extreme service conditions. The investigation focuses on the feasibility studies on the effect of process parameters of Keyhole Plasma Arc Welding (KPAW). The stability of the keyhole on 9 mm thick tubes is by the action of welding current, gas flow rate and the standoff distance. The autogenous joint had a wine glass bead morphology with a minimum heat-affected zone. The influence of current is on the penetration, whereas the gas flow rate and standoff distance govern the geometric appearance. The fusion zone consists of vermicular δ ferrites within the austenitic matrix. The refined vermicular ferrite grains in the fusion zone of the KPAW joint record a maximum strength of 610 MPa and hardness of 230 HV. The failure region reflects the presence of coarse grains; because of the heat dissipation from the fusion zone. The cooling rate is high that it restricts the growth of the grains in the HAZ. The failure is by the ductile manner in KPAW joints.

Keywords:

• Boilers
• super austenite
• plasma
• gas flow

Acknowledgement

The authors are thankful to Science and Engineering Research Board (SERB), Department of Science and Technology (DST) for providing the Plasma Arc Welding (PAW) machine through the funded project (DST/File No: EEQ/2017/000339).

Disclosure statement

No potential conflict of interest was reported by the author(s).