TIG Overlay Welding: 7 Checks Before Specifying a System

TIG overlay welding is a process that deposits a fused layer of metal on a component whose surface requires different properties when compared with its supporting base metal. Relevant information for a sound equipment request begins with the final surface: its alloy, thickness remaining, service environment and the acceptance criteria. The introduced welding speed comes later.

Updated September 2026 · Process and equipment selection guide

What is TIG overlay welding?

TIG overlay welding is a fusion welding process that uses a non-consumable tungsten electrode to deposit filler on a metal surface. TIG denotes tungsten inert gas; its formal process name is gas tungsten arc welding. Shielding gas protects the molten weld pool while the deposited layer adheres to the substrate.

Independent filler and arc control differentiate the TIG process from a consumable-electrode process. Here, the tungsten provides the arc; filler wire supplies the added metal. Select the welding wire for the stipulated deposit. Weld overlay cladding (or weld cladding) deposits metal for surface protection. The base material bears the load within a qualified material combination.

Terminology is important. In its cladding overview, TWI addresses surface protection using deposited materials. Corrosion-resistant weld overlay targets the service condition. Hardfacing addresses resistance to wear; building up a worn dimension, and buttering a dissimilar-metal joint have different objectives.

Enquiry trap: An enquiry trap is when a request for ‘cladding’ alone elicits quotes for multiple jobs. Describe the exposed section and its required function before discussing the machine. A valve sealing face and an eroded shaft may both require additional metal, but the acceptance criteria need not be the same.

Cold wire or hot wire: which TIG cladding process fits?

Filler is fed into the arc region by cold-wire TIG, while hot-wire TIG preheats the wire as it approaches the weld pool. Preheating can reduce the energy the arc needs to completely melt the wire. The comparison relies on torch access, heat control, and the required final deposit.

Conventional resistance heated systems require an external power source to heat the wire. Induction heating is another alternative. Request the supplier to show the heating circuit and its relationship to the workpiece; “hot wire” doesn’t cover all the elements of the cladding system.

A 2026 Hot-wire GTAW cladding study compared induction-heated wire to cold wire of super-austenitic stainless filler on low-carbon steel. Its introduction discusses arc interaction in other heating systems, but that comparison was cited background. The study didn’t show that every resistance heated system suffers from the instability.

To clarify, the illustrative bore-cladding enquiry example includes an offer for flat cladding with a torch opening and another offer for a weld head with torch access to the internal surface. An increase in the quoted deposition rate wouldn’t resolve a collision between the first torch and the bore. Ask both suppliers to illustrate wire feed and torch clearance, and a complete welding sequence on the same drawing.

Weld heads, welding-current controls, and feed controls comprise the process package. The component also must accommodate orbital TIG welding or rotating-head motion. Evaluate the actual configuration of the supplier’s TIG welding machines before considering their headline rates equivalent.

Why does low dilution matter in weld overlay?

Dilution mixes melted base metal with melted filler and changes weld metal chemistry. Using lower dilution may retain the required alloy composition, but is just one of the many acceptance criteria. The other requirements of sound fusion, the remaining clad thickness, and final machined surface must all fulfil the requirements of the intended application.

TWI’s 2010 Alloy 625 overlay investigation found that equal heat input didn’t always produce equal dilution. Its lowest-dilution short-circuit example also had bead geometry that could increase lack-of-fusion risk at overlaps. Those results don’t create a universal dilution limit or show that every low-dilution TIG weld is defective.

Finished-Surface Proof Chain is our editorial worksheet to relate the drawing to the inspected component. Each row shows an evidence handoff, and the acceptance values must be from the governing specification and qualified procedure.

For an illustrative part requiring a 3 mm finished layer, a trial measured at 4 mm before machining leaves an unanswered question. Does the surface still meet the specified chemistry after the planned 1 mm removal? These dimensions demonstrate the lack of evidence and shouldn’t be used as a recommended cladding thickness or machining allowance.

Match the overlay alloy to corrosion and wear

The selection of overlay filler starts with the damage mechanism and the condition of the base-metal. Corrosion resistance, abrasion and high-temperature wear place different requirements on the alloy. Nickel based, cobalt based and carbide containing materials should be considered from a supported service and welding condition, rather than selected because trade names are recognized.

Inconel 625 is a common nickel-alloy example for corrosive service. For other combinations of wear and corrosion, Stellite-type alloys and cobalt hardfacing may be considered. TWI’s materials overview provides some example cases, but doesn’t permit a substitution of one filler for another. For oil and gas field service or for some other application, you need to specify the medium, temperature and the expected mechanism of wear, after which you can request that the relevant welding engineer look into metallurgy.

Keep hardfacing processes in their own category

Other welding methods support other overlay processes. Plasma transferred arc, which is often called PTA welding, is one overlay technique. Gas metal arc welding, including metal inert gas or MIG welding, uses a consumable wire electrode. Submerged arc welding uses flux; shielded metal arc welding, or SMAW, uses coated electrodes. Complex carbide alloys and bronze overlays need their own material and process assessment.

Buyer objection: just because a familiar alloy designation is mentioned doesn’t mean a weld overlay will withstand this service. Please provide your reasoning and the filler you’re proposing as well as any required corrosion, hardness and any other service-related tests. Compatibility and service suitability are separate issues.

Specify the cladding machine around the workpiece

The geometry of the workpiece determines the path of the welding torch and the reachable surfaces as well as how the part can be supported. Different motions may be required for a bore, sealing face and a long shell. Therefore, consider the table below as a request worksheet and submit it along with the actual drawing after checking each proposed arrangement.

Pipe cladding also poses a problem: will the proposed fixture be able to support the required orientation in both vertical and horizontal positions? Confirm that access to all surfaces to be clad is cleared before committing to the motion arrangement.

A reality check comes from a report in a trade magazine on the Polysoude and Arc Energy Resources valve project. In their supplier-origin account, they describe 27-tonne castings that surpassed the lifting capacity of an existing 15-tonne crane. The handling of the castings helped determine the arrangement of the facility. This was their project and was neither an Aubrik production case nor an independent comparative study.

For different aspects of the motion problem, Aubrik’s workpiece rotation and tilt equipment et column-and-boom torch platforms address various motion problem aspects. Turning rolls for cylindrical workpieces are additional options. After confirming the welding process package, load estimations and torch reach, equipment selection can be made.

What evidence should qualify the weld overlay process?

The construction code and the purchaser’s specification and the service criterion will determine the qualification route. Evidence of qualification of the procedure, qualification of persons, and acceptance of production are different levels of evidence. A welding-machine certificate or the appearance of a sample won’t achieve the three elements. Agree on the required records and the test conditions prior to the supplier making a trial deposit.

ISO 15614-7:2016 specifically addresses overlay welding procedure qualification; its public catalogue records confirmation in 2022. The public scope separates build-up repair and dissimilar-metal buttering. Where an ASME construction-code route applies, check the contract’s required edition of BPVC Section IX, publicly listed in a 2025 edition.

ASME’s public QW-484A form is a welder performance qualification record. Its overlay bend and macro-test fields should not be confused with a complete record of procedure qualification or all the requirements for production acceptance. Ensure the relevant procedure, welder and welding-operator qualifications for the actual welding technique are identified by the responsible party.

Substrate integrity is also important. In their 2019 hot-wire GTAW study, Silwal, Walker and West tested resistively heated Inconel 625 filler on 347 stainless steel at primary currents from 60 to 100 A and observed heat-affected-zone cracking in the higher current range. Therefore, a layer that has been formed can’t be viewed in isolation from the material on which it rests. The combination and the conditions that will be present need to be examined through testing.

Safety is dictated by both the materials and the workplace. NIOSH’s welding ventilation guidance outlines the risks of alloy dependent fume hazards and includes nickel chromium bearing materials. OSHA’s welding-fume factsheet states that shielding gases can displace oxygen. Low visible fumes don’t lessen the requirement for assessing exposure, ventilation, or the proper control of confined spaces.

Position should also have a place in trial records. Aubrik’s plate and pipe welding-position guide describes the language; it’s the applicable qualification rules that determine what positions are included.

Compare cost per accepted clad component

The cost per accepted clad component is the total batch cost divided by the number of parts that meet the predetermined release criteria. The cost of process setup, deposition, finishing, inspection and the cost of unsuccessful work should be included. The accounting boundary should be kept constant for both costs. Assumptions regarding capacity and service life should be analyzed separately from this batch cost.

“But it’s really not a simple matter of one welding process outpacing another.”

This point is made in the discussion about joining/changing over. It isn’t a benchmark with a measured cladding-cost. Their supplier affiliation matters. Other, separate research on wire-arc additive manufacturing costs explains why batch size and post-processing should be included within the costing boundary stated. Its prices aren’t TIG overlay prices.

The inputs were made up for this example; this isn’t an Aubrik quote or factory output. Both routes face the same end requirement. At the conclusion of the case, Route B’s two unaccepted elements continue to be rejected and the cost of the processing is retained within the total of Route B. The costs for transportation, tax, purchase of equipment, and the cost of the service life of the parts lie outside the total for both routes.

The arithmetic is $3,000 ÷ 20 = $150 per accepted part, against $3,420 ÷ 18 = $190. Although Route B spends $300 less on arc work, its extra downstream costs and lower accepted output reverse the apparent advantage. Procurement is to set the same accounting boundary; quality is to set acceptance; production is to record the time elapsed and changeover.

Goulet d'étranglement caché : The faster deposition can feed a machining or inspection queue that can’t release parts any faster. A hybrid additive component repair study further separates the cost of local repair from the cost of wider supply-chain considerations. Use this batch worksheet as one comparison, in addition to delivery, capacity and ownership costs.

Turn TIG welding automation claims into a testable enquiry

A testable tig welding request includes a real component drawing along with a defined process package and an acceptance plan. Separate workholding and motion from welding power, filler heating, shielding and inspection. Describe who supplies and qualifies each of the elements and request supporting documentation for the necessary weld overlay activities.

The 2026 induction-heated cladding study poses many useful questions about the heating process, the geometry of the bead, and the testing of materials. It doesn’t set a precedent for the productivity of the market as a whole. Automated TIG weld overlay should be able to justify its existence based on the results of a trial, rather than the age of a controller or a welding speed claim in isolation.

• Identify the base material, filler specification, and the surface to be clad.
• Supply component dimensions, mass, center of gravity, and fixture access.
• Define the finished layer, machining sequence and service conditions.
• Name the governing specification, qualification route and release evidence.
• Express batch mix, changeover, and required accepted output.
• Assign responsibility for process integration, training and site controls.

Aubrik has published a scope that allows discussion on positioning and torch-manipulator systems. A complete qualified TIG overlay process must be confirmed in the agreed supply package. Send Aubrik your component drawing and overlay requirements to initiate that scope discussion, relative to the welding-manipulator range as the torch-platform reference.

Questions fréquemment posées

TIG overlay process questions often merge issues of process speed, surface protection and equipment selection. The responses below separate the issues involved. Process vocabulary may stimulate a request, but the required materials, geometry and acceptable completed part will define the comparison of welding equipment and the selection of the process service provider.