Mechanical characterization of 18% Ni maraging steel welds produced by cold wire and hot wire gas tungsten arc welding

Abstract

Maraging steels are a distinct class of ultra-high-strength alloys extensively employed in the fabrication of solid rocket motor casings. These casings are typically manufactured in segmented form, with the desired mechanical properties achieved through controlled ageing heat treatment. Since the design of such pressure vessels is governed by fracture mechanics criteria, obtaining adequate tensile and fracture toughness properties in weldments is critical. Although these steels exhibit good weldability and can be joined successfully using Gas Tungsten Arc Welding (GTAW), the conventional process is limited by low welding speeds and deposition rates, making it less suitable for thicker sections. To overcome these limitations, the Hot Wire Gas Tungsten Arc Welding (HW-GTAW) process was adopted. The filler wire is resistance-heated prior to melting, leading to improved deposition rates, better weld pool fluidity, and enhanced productivity. This study compares the tensile strength, fracture toughness, hardness, and hydrogen content of 18% Ni maraging steel welds produced by HW-GTAW and Cold Wire GTAW (CW-GTAW). Bend tests were also conducted to evaluate weld integrity. Results demonstrate that HW-GTAW produces sound, porosity-free welds with superior mechanical properties and with approximately 25% higher productivity.