Weld Overlay and Cladding Procedures

A corrosion resistant overlay is intended to deliver the specified alloy properties at the required location within the finished deposit. Hardfacing is selected primarily for a wear mechanism. The qualification and acceptance requirements must reflect that purpose rather than relying solely on a conventional groove weld qualification.

Dilution occurs when melted base metal mixes with the deposited filler metal. This can change the overlay chemistry, particularly in the first layer. The required alloy composition may therefore depend on the welding process, parameters, bead overlap, layer sequence and remaining thickness after machining. Additional layers can reduce the base metal's influence, but layer count alone is not proof of acceptable chemistry.

The procedure must identify the finished thickness and the location at which chemistry or hardness is assessed. When chemical analysis is required, the sampling plane must represent the specification requirement and the material remaining in service. A filler metal certificate cannot establish the chemistry of a diluted deposit.

A groove weld qualification should not be assumed to cover corrosion resistant overlay or hardfacing. HCR reviews the applicable qualification rules and application requirements to determine the correct coupon and test program.

Nickel and stainless overlays can protect carbon and low alloy steel components while retaining the base material's structural function. Alloy selection depends on the fluid, temperature and degradation mechanism, together with the required deposit chemistry and compatibility with subsequent heat treatment.

The alloy scope identified for these pages includes Alloy 625, Alloy 622 and Alloy 825, along with stainless grades 316/316L, 308/308L, 347 and 309/309L. Their suitability is evaluated individually. These materials are not interchangeable solutions for chlorides, sour service, seawater or elevated temperature exposure.

Typical applications include valve components, bores, pressure equipment and other wetted surfaces. Base material specifications and any sour service requirements must be reviewed before welding. HCR considers dilution, finished thickness, thermal history and inspection requirements together so that the procedure addresses the actual component and service environment.

Hardfacing addresses wear mechanisms such as sliding contact, galling, abrasion or erosion. A deposit suitable for one mechanism may be unsuitable for another, especially when impact, temperature or corrosion is also involved.

HCR's stated hardfacing scope includes Stellite 6, Stellite 21 and other alloys selected after reviewing the application. Typical locations include valve gate and seat surfaces, seal faces and other wear surfaces. The selection must account for the base metal, weldability, required hardness, deposit integrity and final machining or grinding requirements.

The qualification plan may include hardness measurements, macro examination, chemistry or application specific testing, as required by the governing standard and specification. Acceptance criteria for corrosion resistant overlay should not be carried over automatically to hardfacing. HCR defines the intended function and acceptance requirements before qualification or repair begins.

An overlay PQR should document the actual qualification conditions and the tests required for the selected overlay category. Essential information includes base material identification, filler metal traceability, process and welding parameters, preheat, interpass temperature, thermal treatment and deposited thickness.

For corrosion resistant overlay, chemical analysis is performed at the location required by the applicable code or specification. The test plan should distinguish deposited thickness, machining allowance and the minimum overlay remaining on the finished component. Chemistry accepted at one sampling depth does not automatically demonstrate compliance at every depth.

Guided bend tests, macro examination, hardness surveys and NDE are included where required. A hardness traverse can assess the overlay, heat affected zone and base metal when specified. Tests and acceptance criteria differ between corrosion resistant overlay, hardfacing and dimensional build up.

The client package brings together the PQR, supported WPS, relevant laboratory and examination reports, material and consumable records, and any specified macro photographs. This provides traceable qualification evidence; additional service performance testing may be needed if the specification requires it.

After the procedure is established, HCR can support production overlay, bore cladding, hardfacing, dimensional build up and machining to the required dimensions. Planning these operations together helps preserve the required deposit thickness after finishing and reduces coordination between welding and machining suppliers.

The stated minimum bore diameter is 3 inches, subject to bore length, tooling clearance, weld access and inspection access. Larger components are reviewed against the proposed setup. Shop fabrication and field repair are evaluated separately because preparation, environmental controls and component accessibility can differ substantially.

Before execution, HCR reviews the component drawing, material condition, finished dimensions, inspection plan and applicable procedure. Repair work also requires an assessment of the existing deposit and underlying material.