RTJ Groove Cladding & Weld Overlay Services

RTJ groove cladding is the application of a corrosion- and erosion-resistant weld overlay — most often Inconel 625 — onto the ring-type-joint (RTJ) sealing groove of a flange, which is then machined back to the original ring number and finish. It protects or repairs the sealing surface so the flange resists corrosion, lasts longer and seals reliably.

Inconel 625 (Alloy 625) is the industry default because it combines outstanding resistance to chlorides, sour gas (H₂S) and a wide range of acids with high strength and excellent weldability. It bonds metallurgically to carbon and low-alloy steel flanges and meets NACE MR0175 for sour service, so the sealing surface stays sound in aggressive oil & gas and offshore media.

Yes. Corroded, pitted, eroded or galled RTJ grooves are routinely repaired by machining out the damage, depositing a weld overlay, and re-machining the groove to its original ring number and surface finish. Repair restores a leak-tight sealing surface at a fraction of the cost and lead time of a new flange.

The common overlay alloys are Inconel 625, Monel 400, Duplex 2205, Super Duplex 2507, Hastelloy C276, Stellite 6 (for hardfacing) and 316L stainless steel. The choice depends on the service — Inconel 625 for sour/chloride media, Monel for seawater and HF acid, duplex/super duplex for high-chloride strength, Hastelloy for strong acids, and Stellite where wear and galling resistance matter most.

A finished corrosion-resistant overlay is typically about 3 mm (1/8 inch) thick after machining, and codes such as NACE MR0175 commonly require a minimum of around 3 mm of overlay at the sealing surface. More material is deposited before machining to allow for blending and final cut. The exact thickness is set by the specification and the depth of damage being repaired.

RTJ groove dimensions follow ASME B16.5, ASME B16.47, API 6A and API 17D, with ring grooves to ASME B16.20 / API 6A ring numbers (R, RX, BX). Welding is qualified to ASME Section IX (WPS/PQR), and sour-service work follows NACE MR0175 / ISO 15156. Material and overlay are documented with EN 10204 3.1 certificates.

Yes. When specified, RTJ groove overlays are produced to NACE MR0175 / ISO 15156 for sour (H₂S) service — using qualified alloys such as Inconel 625, controlled welding procedures, a compliant minimum overlay thickness and hardness control. NACE-compliant documentation is provided with the flange.

Yes. Stellite 6 (a cobalt-chromium hardfacing alloy) is applied to RTJ grooves where wear, galling and high-temperature erosion are the main concern — for example on valve and high-cycle sealing surfaces. Stellite gives an extremely hard, wear-resistant sealing face, and can be combined with a corrosion-resistant buffer layer where needed.

RTJ groove repair restores the existing flange by cladding and re-machining only the damaged sealing surface, keeping the original forging, bolt holes and bore. Replacement means scrapping the flange and buying a new one — far more expensive and with a long lead time, especially in exotic alloys or large bores. Repair is usually the faster, lower-cost option when the flange body is sound.

A typical RTJ groove refurbishment runs from a few days to about two weeks, depending on size, alloy, heat-treatment needs and inspection scope. This is dramatically faster than the multi-week or multi-month lead time for a new forged flange in an exotic alloy — which is why repair is favoured during turnarounds and shutdowns.

Yes. After the overlay is deposited, the groove is CNC-machined back to the exact ring number, groove width, depth, angle and surface finish required by ASME B16.5 / API 6A, so the refurbished flange seals identically to a new one and accepts a standard RTJ ring gasket.

After overlay and machining we use visual inspection, dye-penetrant (PT) and/or ultrasonic (UT) testing for weld soundness, PMI (positive material identification) to confirm the alloy, hardness testing, and dimensional inspection against the RTJ ring standard. Results are recorded in the quality dossier supplied with the flange.

Oil & gas, offshore platforms, subsea equipment, refineries, petrochemical and chemical plants, LNG facilities, power plants and shipbuilding all use RTJ groove cladding — anywhere high-pressure RTJ flanges face corrosive or sour media and need a durable, leak-tight sealing surface.

Yes. Offshore and subsea RTJ flanges are ideal candidates for refurbishment: their large bores and exotic alloys make replacement very costly and slow, while cladding and re-machining the groove restores sealing performance quickly and to the same code, keeping platforms and turnarounds on schedule.

Repairing the groove typically costs a fraction of a new flange — often 40–70% less — because you reuse the existing forging and only clad and machine the sealing surface. The saving grows with size and alloy: a large-bore Inconel-overlaid flange repair can save the majority of the cost of an equivalent new forged item, plus weeks of lead time.

A ring-type-joint (RTJ) flange has a precision-machined groove that holds a metal ring gasket (R, RX or BX type). Bolting up compresses the ring into the grooves of both flanges, creating an initial line-contact seal that tightens under pressure — the standard high-pressure, high-temperature sealing method in oil & gas and process plants.

Corrosion-resistant overlays are usually deposited by GTAW (TIG), including hot-wire TIG, for a clean, low-dilution, high-quality deposit on the sealing surface. Other processes such as PTA or wire-arc may be used for hardfacing or larger areas. All welding is to qualified WPS/PQR under ASME Section IX by certified welders.

Yes. We provide RTJ groove cladding both as a repair/refurbishment service for in-service flanges and as new manufacture — supplying brand-new flanges with a corrosion-resistant overlaid (clad) RTJ groove, which is far more economical than a solid exotic-alloy flange.

We overlay and machine the full range of RTJ ring numbers — R and RX (oval/octagonal, per ASME B16.20) and BX (per API 6A) — across ASME B16.5, ASME B16.47 and API 6A / 17D flange sizes and pressure classes, and to custom dimensions on request.

Every overlaid sealing surface is checked by PMI (positive material identification) using XRF or optical emission, confirming the deposited chemistry matches the specified alloy (for example Inconel 625) across the finished groove. The PMI report is included in the documentation package.

The machined RTJ groove is finished to the surface roughness required by ASME B16.5 / API 6A for ring-joint sealing surfaces — typically around 63 microinch Ra or finer — so the metal ring gasket seats and seals correctly. The exact finish is confirmed during dimensional inspection.

No. A correctly applied overlay bonds metallurgically to the base flange and the groove is machined back to standard dimensions, so the flange retains its original pressure class and rating. The overlay adds corrosion/erosion protection to the sealing surface without reducing the flange's structural capacity.

Yes. Besides Inconel 625, we overlay grooves with Monel 400 (seawater, HF acid), Duplex 2205 and Super Duplex 2507 (high-chloride strength), and Hastelloy C276 (strong acids and chlorides). The alloy is selected to match the process medium, temperature and corrosivity.

Yes. The package can include EN 10204 3.1 material test certificates, welding procedure and qualification records (WPS/PQR to ASME IX), PMI reports, NDE (PT/UT) reports, hardness results, dimensional inspection reports and NACE MR0175 compliance statements — with third-party inspection (BV, SGS, Lloyd's, TÜV) on request.

Send your flange drawing or RTJ ring number, the overlay alloy and standard (e.g. Inconel 625, NACE MR0175, API 6A), the quantity, and your delivery location. Tesco Steel & Engineering will respond with a competitive quote and lead time, for both repair/refurbishment and new clad-flange manufacture.