Incoloy 925 (UNS N09925) is welded with INCO-WELD® Filler Metal 725NDUR (UNS N07725) when matching strength is required, or with INCONEL® Filler Metal 625 (UNS N06625) when solid-solution overmatching is preferred. The alloy is weldable by all common arc processes, GTAW (TIG), GMAW (MIG), SMAW (stick) and SAW (submerged arc). Welding in the solution-annealed condition is preferred; aged material can be welded but the heat-affected zone (HAZ) requires post-weld solution anneal + age cycle to recover gamma-prime strengthening. The qualified Charpy and tensile data in Special Metals Table 12 form the basis for weld procedure qualification per ASTM B805 Section 9 and ASME IX.
Need welded Incoloy 925 fabrications? Email info@torqbolt.com with drawing, base/filler combination and required post-weld heat treatment. TorqBolt issues weld procedure qualification records (WPQR) per ASME IX on request, with welder qualification records (WQR) for each operator. WhatsApp +91-22-66157017.
Filler Metal Selection
| Filler | UNS | AWS Class | Use Case |
|---|---|---|---|
| INCO-WELD® 725NDUR | N07725 | ERNiCrMo-15 (GTAW/GMAW) | Matching-strength welds; preferred for API 6A components |
| INCONEL® Filler Metal 625 | N06625 | ERNiCrMo-3 (GTAW/GMAW), ENiCrMo-3 (SMAW) | Solid-solution overmatching; corrosion-resistant overlay; dissimilar-metal welds |
| INCONEL® Filler Metal 686 | N06686 | ERNiCrMo-14 | Severe sour-service overlay (over-alloyed corrosion barrier) |
For sour-service production, INCO-WELD 725NDUR is the standard filler, it ages with the same gamma-prime kinetics as the parent metal, giving full mechanical-property recovery after post-weld solution anneal + age. Inconel 625 is preferred for dissimilar-metal welds (Incoloy 925 to carbon steel, duplex stainless, etc.) where ageing the joint is impractical.
Welding Process, Recommended Parameters
| Process | Current | Polarity | Shield Gas | Heat Input |
|---|---|---|---|---|
| GTAW (TIG) | 80–200 A | DCEN | Argon (welding-grade, ≤20 ppm O₂) | 0.5–1.5 kJ/mm |
| GMAW (MIG) | 180–350 A | DCEP | Argon + 1–5% CO₂ (NOT 100% CO₂) | 0.8–2.0 kJ/mm |
| SMAW (stick) | 80–180 A | DCEP | (electrode coating) | 1.0–2.5 kJ/mm |
| SAW | 300–500 A | DCEP | (neutral basic flux) | 2.0–4.0 kJ/mm |
Heat input must be controlled. Above ~2.5 kJ/mm, weld-pool dilution and HAZ grain coarsening reduce Charpy toughness below the 40 J / 30 ft-lb sour-service acceptance criterion. The maximum interpass temperature is 350°F (175°C); higher interpass temperatures cause secondary gamma-prime precipitation in the HAZ that embrittles the joint.
Pre-Weld & Interpass Conditions
- Pre-weld condition: Solution-annealed material strongly preferred. Aged material can be welded but the HAZ over-ages, reducing strength, this requires full post-weld solution anneal + age to recover.
- Preheat: Not required. 70°F (21°C) ambient acceptable. Avoid moisture and oil contamination on the joint surface.
- Joint cleanliness: Mechanically clean to bright metal within ±25 mm of the weld zone. Solvent-wipe with acetone before tacking. Sulfur, lead, copper, zinc and chlorine contamination must be excluded, these elements cause hot cracking in nickel alloys.
- Interpass temperature: 350°F (175°C) maximum. Cool naturally between passes; do not force-cool with water or compressed air.
- Backing gas: Argon or argon + 5% hydrogen for root-pass purging on root-side-inaccessible joints (NOT for ferritic-side dissimilar welds, H₂ can embrittle).
Post-Weld Heat Treatment
For full mechanical-property recovery, the welded assembly is given the same heat-treatment cycle as the parent metal:
| Step | Temperature | Hold Time | Cooling |
|---|---|---|---|
| 1. Solution Anneal | 1900°F (1040°C) | 1 h per 1" thickness, min 1 h | Water Quench |
| 2. Age (Step A) | 1365°F (740°C) | 8 h | Furnace cool 100°F/h to 1150°F |
| 3. Age (Step B) | 1150°F (621°C) | 8 h | Air Cool |
For thick-section welds (above 2" / 50 mm), an intermediate stress-relief at 1100°F (593°C) for 4 hours is recommended between the weld and the solution anneal. This relieves residual welding stress before the high-temperature anneal cycle. See full heat-treatment page for furnace control requirements.
Charpy V-Notch Impact, Welded vs Parent (Per Special Metals Table 12)
| Pre-weld Condition | Process | Post-weld Treatment | Charpy at +20°C | Charpy at -50°C |
|---|---|---|---|---|
| Annealed | GTAW | Anneal + Age | 57 J (42 ft-lb) | 45 J (33 ft-lb) |
| Annealed | GMAW | Anneal + Age | 47 J (35 ft-lb) | 38 J (28 ft-lb) |
| Annealed | SMAW | Anneal + Age | 40 J (30 ft-lb) | 32 J (24 ft-lb) |
| Aged (no PWHT) | GTAW | Age only (re-age) | 26 J (19 ft-lb) | 18 J (13 ft-lb) |
| Aged (no PWHT) | GMAW | Age only (re-age) | 27 J (20 ft-lb) | 19 J (14 ft-lb) |
The takeaway: welding in the annealed condition followed by full PWHT (anneal + age) gives Charpy values well above the 40 J / -50°C sour-service threshold. Welding in the aged condition with re-ageing only (no solution anneal) drops Charpy below the threshold and is NOT acceptable for API 6A wellhead service.
Tensile Properties of Welded Joints
Per Special Metals Figures 7–12, transverse-tensile coupons of welded Incoloy 925 (anneal + GTAW + PWHT anneal + age) consistently fail in the parent metal at 165–175 ksi (1140–1207 MPa) UTS, indicating full strength recovery in the weld and HAZ. INCO-WELD 725NDUR weld metal has slightly higher yield strength than the parent metal in the aged condition (~115 ksi vs ~110 ksi), giving overmatched joints, the preferred condition for fatigue-loaded applications.
Welding Defects & Common Issues
Hot cracking: Caused by sulfur, lead, copper or zinc contamination at the joint surface. Always solvent-wipe before welding. If the parent metal has been exposed to galvanised tooling or copper backing bars, allow 25 mm cut-back before edge preparation.
Microfissuring in HAZ: Caused by excessive heat input or interpass temperature above 175°C. Reduce travel speed, increase number of passes, allow longer cool-down between passes.
Lack of fusion: Common with INCO-WELD fillers because they are sluggish in the puddle. Compensate with slightly higher current and slower travel; do not increase voltage (causes spatter and undercut).
Porosity: Caused by moisture or organic contamination. Pre-bake SMAW electrodes at 350°F for 2 hours; store filler wire in dry conditions; ensure shielding-gas purity (welding-grade argon, ≤20 ppm O₂).
Welding Standards Compliance
- ASME IX: Procedure qualification (PQR), procedure specification (WPS) and welder performance (WQR) for Incoloy 925 falls under P-No 45, Group 2 (nickel alloys).
- ASTM B805 Section 9: Weld coupons must be tested per ASTM E8 (tensile), ASTM E23 (Charpy) and meet 100% of the parent-metal limits.
- API 6A Annex M: Weld procedures for wellhead and Christmas tree components must be qualified at the maximum heat input of the production weld; impact-tested at -29°C minimum (PSL 3) or -46°C (PSL 3G).
- NACE MR0175 / ISO 15156: Welds must demonstrate ≤35 HRC across the entire HAZ + weld metal in the final heat-treated condition.
Frequently Asked Questions
Can Incoloy 925 be welded to carbon steel? Yes, with INCONEL Filler Metal 625 (or 686 for severe sour service). Dissimilar welds should NOT be solution annealed because the carbon steel side will distort or harden uncontrollably; instead, weld the joint in the carbon-steel side's normalised condition with a low-stress procedure and accept the as-welded HAZ on the Incoloy 925 side.
Is preheat ever required? No. Incoloy 925 has no martensitic transformation and no hydrogen-cracking susceptibility, preheat is not required. Excessive preheat is actively harmful because it raises interpass temperature above 175°C and causes HAZ over-ageing.
What is the difference between INCO-WELD 725NDUR and INCONEL 625 for this alloy? 725NDUR matches the parent-metal chemistry (Ni-Cr-Mo-Ti) and ages to similar strength. 625 is a solid-solution Ni-Cr-Mo-Nb alloy that does NOT age-harden, it gives a softer, more ductile weld metal but cannot be brought to 110 ksi YS by post-weld ageing. Use 725NDUR for matching-strength API 6A welds; use 625 for corrosion-resistant overlay or dissimilar joints.
Does TorqBolt qualify weld procedures for customers? Yes. We hold WPQRs per ASME IX for GTAW, GMAW and SMAW of Incoloy 925 with INCO-WELD 725NDUR and INCONEL 625 fillers. Customer-specific procedures qualified on request, specify base material thickness, joint geometry, position and pre-/post-weld treatment requirements.
Request a Quote
For welded Incoloy 925 fabrications with WPQR / WQR documentation:
- Email: info@torqbolt.com
- WhatsApp: +91-22-66157017
- WPQR + sample WQR + sample MTC available on request
Specify drawing / sketch, base material specification (ASTM B805 bar / ASTM B983 plate), filler-metal selection, weld process (GTAW / GMAW / SMAW / SAW), joint configuration, applicable code (ASME IX / API 6A / NACE MR0175), pre-/post-weld heat treatment requirements, and any third-party witness needed for the WPQR.
References: Special Metals Corporation: INCOLOY® alloy 925 Technical Bulletin, Table 12, Figures 7–12. ASTM B805 Section 9 Weld Procedure Qualification. ASME IX Welding and Brazing Qualifications. API Specification 6A Annex M. AWS A5.14 Filler Metal Specification. INCO-WELD®, INCOLOY® and INCONEL® are registered trademarks of Special Metals Corporation.
