Testing Information
ZHONGXI Testing provides weld failure analysis, a systematic engineering investigation service that determines why a welded joint, weldment, or welded structure fractured, cracked, leaked, corroded, or otherwise failed to perform its intended function. Weld failure analysis is applied across pressure vessels and boilers, pipelines for oil and gas transport, shipbuilding hulls and stiffeners, structural steel for buildings and bridges, automotive and rail car bodies, aerospace components, stainless steel process piping, aluminum alloy frames, and nickel-alloy reactor internals. The analysis identifies the root cause of the failure, whether it originates from welding process defects, base metal or filler metal deficiencies, improper heat treatment, design-induced stress concentration, service overloading, fatigue, hydrogen embrittlement, corrosion, or a combination of these mechanisms.
The purpose of weld failure analysis is to reconstruct the sequence of events to fracture, to characterize the failure mode (ductile overload, brittle cleavage, fatigue, creep, stress corrosion cracking, hydrogen-induced cracking, liquid metal embrittlement, corrosion fatigue, or weld defect propagation), and to attribute the failure to a specific metallurgical or mechanical origin so that corrective actions can be defined. The technical evaluation integrates fracture surface examination by scanning electron microscopy, energy-dispersive X-ray spectroscopy for micro-area composition, metallographic sectioning to reveal weld penetration, fusion boundary condition, heat-affected zone microstructure, grain size and inclusions, microhardness mapping across the weld cross-section, chemical composition verification of base metal, weld metal and filler wire, residual stress measurement, and mechanical testing of the joint including tensile, bend, impact and fatigue characterization. Non-destructive methods such as radiographic testing, ultrasonic testing, magnetic particle testing and penetrant testing are used at the preliminary stage to locate internal and surface discontinuities before destructive sectioning.
A typical analysis workflow begins with visual examination and photographic documentation of the failed component, followed by non-destructive inspection to map defects, then fracture surface protection and controlled sectioning. The fracture surface is studied at low magnification by stereomicroscopy to identify the crack initiation site, propagation direction and final fracture zone, then by SEM fractography at magnifications from roughly 20× to 10,000× to resolve dimple rupture, cleavage facets, fatigue striations, intergranular facets, quasi-cleavage, or river patterns. Cross-sections through the initiation region are polished and etched with reagents such as nital for carbon and low-alloy steels, glyceregia or aqua regia for stainless steels, and Keller's reagent for aluminum alloys, revealing lack of fusion, incomplete penetration, hot cracks, cold cracks, lamellar tearing, slag inclusions, porosity, and sensitized or carburized zones. Core parameters evaluated include weld penetration depth, fusion zone width, heat-affected zone width, phase balance in duplex stainless welds, ferrite content in austenitic weld metal, microhardness traverse values, inclusion ratings, grain coarsening, decarburized layer depth, hydrogen content in weld metal, and Charpy impact energy at the fusion line. The final technical evaluation correlates all observed evidence into a failure mechanism determination and distinguishes between manufacturing-related causes, material-related causes, and service-related causes.
The scope of the work also covers weld procedure qualification failures, production weld reject analysis, dissimilar metal joint failures, repair weld cracking, and post-weld heat treatment problems such as stress-relief cracking or reheat cracking in creep-resistant steels like 2.25Cr-1Mo and Grade 91. Depending on the failure mechanism identified, supplementary tests such as hydrogen determinations by inert gas fusion, sulfide inclusion mapping, corrosion product analysis by X-ray diffraction, and elevated-temperature tensile or creep rupture testing of the weldment may be added to complete the evidence chain.
FAQ
How long does weld failure analysis take?
The standard turnaround is 7-15 working days, depending on the number of test items selected and the sample type. Simple fracture mode determination with fractography and metallography is usually completed within about one week, while comprehensive analyses involving fatigue testing, residual stress depth profiling, creep damage assessment, multiple section metallography or supplementary chemical work can require ten to fifteen working days. Urgent projects can be scheduled with expedited sequencing, and a preliminary verbal finding on the failure mode is often available after the fractography stage.
How is the cost of weld failure analysis determined?
Cost is determined by the number of testing items included in the plan. A basic package covering visual examination, SEM fractography, metallographic sectioning and microhardness traverse is priced lower than a full program adding composition analysis, diffusible hydrogen measurement, residual stress mapping, Charpy impact testing or fatigue verification. Because each failure case has a different evidence requirement, the laboratory engineers review the failed part, the service history and the questions to be answered, then issue a quotation listing the selected items and fees before work begins.
Which test items does weld failure analysis include, and how much sample should be prepared?
The included items depend on the weld type, the base material and the applicable standards. For arc-welded steel joints, the core items usually cover fracture surface examination by stereomicroscope and SEM, cross-section metallography of the crack path, microhardness traverse, chemical composition of base and weld metal, and defect characterization; aluminum and stainless joints add phase and inclusion analysis, while high-strength steels add diffusible hydrogen testing. For sampling, if the failed component can be cut, a section of roughly 100-500 g containing the complete fracture surface plus sound reference weld is sufficient; if the whole part must be submitted, the laboratory performs the sectioning in-house under fracture surface protection.
Can weld failure analysis distinguish a manufacturing defect from a service-induced failure?
Yes, this distinction is a central objective of the analysis. Manufacturing-related failure typically shows crack initiation at internal lack of fusion, porosity, slag or hot cracks, with fractographic and metallographic evidence that the discontinuity formed during solidification or immediately after welding. Service-related failure usually initiates at stress concentrations such as the weld toe or root and propagates by fatigue striations, corrosion pits, creep cavities or ductile overload features, with crack path morphology consistent with sustained or cyclic loading. Microhardness anomalies, HAZ microstructure and composition data further separate improper heat treatment or wrong filler metal from operational causes.
Testing Instruments
- Scanning electron microscope (SEM) with secondary electron and backscattered electron detectors for fractography at magnifications up to 100,000×
- Energy-dispersive X-ray spectrometer (EDS) attached to SEM for micro-area elemental analysis of inclusions, oxides and corrosion products
- Stereomicroscope with 5× to 80× zoom for low-magnification fracture surface survey and weld profile documentation
- Optical emission spectrometer (OES) for quantitative chemical analysis of steels, stainless steels, aluminum and copper alloys
- Inert gas fusion hydrogen, oxygen and nitrogen analyzer for diffusible and residual hydrogen measurement in weld metal
- Carbon and sulfur infrared analyzer for combustion-based determination of C and S content linked to hot cracking susceptibility
- Metallographic microscope with bright-field, polarized light and DIC illumination for microstructure examination at 50× to 1000×
- Image analysis for grain size measurement, phase ratio determination, inclusion rating and porosity quantification
- Micro-Vickers hardness tester with loads from 10 gf to 1 kgf for hardness traverses across weld zones
- Vickers and Rockwell bench hardness testers for bulk hardness of base metal and weld metal
- Portable Rockwell and Leeb hardness tester for on-site hardness checks on in-service welded structures
- X-ray diffraction (XRD) instrument for residual stress measurement and corrosion product phase identification
- Universal testing machine with capacities up to 1000 kN for transverse weld tensile, all-weld-metal tensile and bend tests
- Charpy impact tester with instrumented tup for impact energy and fracture behavior at temperatures from -196 °C to ambient
- Electro-hydraulic servo fatigue testing machine for high-cycle and low-cycle fatigue characterization of welded joints
- X-ray fluorescence analyzer (XRF) for rapid non-destructive composition screening and alloy grade verification
- Digital radiography (DR) and industrial computed tomography (CT) for internal porosity, lack of fusion and crack imaging before sectioning
- Ultrasonic flaw detector with phased array and TOFD capability for weld seam inspection and crack depth sizing
- Magnetic particle inspection equipment for surface and near-surface crack detection in ferromagnetic weldments
- Color penetrant inspection line for surface crack reveal on non-magnetic alloys such as stainless steel and aluminum
- Grinding, polishing and etching sample preparation line including hot mounting press and automatic polisher
- Low-temperature etching and electrolytic polishing unit for austenitic and duplex stainless steel metallography
Testing Items
- Weld penetration depth — measures how far fusion extends into the root, with insufficient penetration acting as a crack initiation notch under cyclic loading
- Heat-affected zone width — defines the region of microstructural transformation and property gradient caused by the weld thermal cycle
- Microhardness traverse — maps hardness from base metal through the HAZ to weld metal to detect softening, hardening or untempered martensite
- Lack of fusion assessment — identifies planar discontinuities at weld interfaces that act as pre-existing cracks under tensile stress
- Porosity content and distribution — quantifies gas cavities that reduce load-bearing cross-section and fatigue life
- Slag inclusion rating — evaluates entrapped non-metallic particles that create stress raisers and local brittleness
- Hot crack (solidification cracking) evaluation — detects interdendritic cracks formed during weld metal solidification, common in high-sulfur steels and austenitic welds
- Cold crack (hydrogen-induced cracking) evaluation — identifies delayed cracking in the HAZ driven by diffusible hydrogen, hard microstructure and restraint stress
- Lamellar tearing assessment — detects step-like cracking under through-thickness tensile stress in rolled plate containing elongated sulfide inclusions
- Reheat cracking evaluation — examines intergranular cracking in coarse-grained HAZ of creep-resistant steels during post-weld heat treatment or service
- Fatigue striation analysis — measures striation spacing on the fracture surface to estimate crack growth rate and cyclic stress range
- Fracture mode determination — distinguishes ductile dimple rupture, cleavage, intergranular separation and quasi-cleavage by SEM fractography
- Crack initiation site localization — pinpoints whether failure started at the weld toe, root, fusion line, internal defect or base metal
- Ferrite content in austenitic weld metal — measured by point count or magneto-inductive methods, typically targeted at 3-10 FN to balance hot cracking resistance and corrosion resistance
- Phase balance in duplex stainless welds — verifies approximately 50/50 austenite-ferrite ratio, since excess ferrite degrades toughness and corrosion performance
- Sensitization and intergranular corrosion susceptibility — detects chromium carbide precipitation at grain boundaries in 304/316 weld HAZ
- Diffusible hydrogen content — measured by gas chromatography or mercury method; values above roughly 5 mL/100 g indicate elevated hydrogen cracking risk in high-strength welds
- Chemical composition verification — optical emission or combustion analysis of base metal, weld metal and filler to check dilution, carbon equivalent and tramp elements
- Carbon equivalent calculation — evaluates C, Mn, Cr, Mo, V, Ni and Cu content against CE or Pcm formulas to judge weldability and preheat requirement
- Grain size and coarsening in the HAZ — coarse austenite grains near the fusion line reduce toughness and raise brittle transition temperature
- Inclusion rating and morphology — sulfide and oxide stringers measured per inclusion cleanliness charts to assess lamellar tearing and fatigue sensitivity
- Decarburized layer depth — surface carbon loss in the weld region reduces hardness and wear or fatigue resistance
- Residual stress distribution — measured by X-ray diffraction, hole-drilling or contour methods; high tensile residual stress accelerates stress corrosion and fatigue cracking
- Weld misalignment and distortion measurement — quantifies angular distortion, offset and gap that create secondary bending stresses
- Weld toe radius and reinforcement geometry — sharp toe radii concentrate stress and dominate fatigue strength of as-welded joints
- Corrosion product and oxide layer analysis — identifies chlorides, sulfides or high-temperature oxides by EDS and XRD to confirm corrosion-assisted mechanisms
- Liquid metal embrittlement evidence — detects copper or zinc penetration along steel grain boundaries during welding of contaminated or coated surfaces
- Creep cavity and creep damage assessment — evaluates cavitation and carbide coarsening in long-service Grade 91 and 2.25Cr-1Mo welds
- Charpy impact energy at fusion line and HAZ — quantifies toughness of individual weld zones at service or low temperature
- Tensile strength and bend ductility of the joint — verifies whether the weld or HAZ is the weak link relative to the base metal specification
Testing Scope
- Butt welds in carbon steel plates (Q235B, Q345B, Q355B, Q420, Q460) with arc welding processes
- Butt welds and girth welds in pipeline steels (X52, X60, X65, X70, X80) for oil and gas transmission lines
- Submerged arc welded longitudinal seams in LSAW and ERW line pipe and spiral-welded pipe
- Pressure vessel and boiler welds in Q245R, Q345R, Q370R, 15CrMoR, 12Cr1MoVR and SA-387 Gr.22 plate
- Grade 91 (10Cr9Mo1VNbN) and Grade 23 creep-resistant steel weldments in power plant main steam piping
- Austenitic stainless steel welds in 304, 304L, 316, 316L, 317L, 321 and 347 piping and vessels
- Duplex stainless steel welds in 2205 (S31803/S32205), 2507 (S32750) and lean duplex 2304
- Nickel alloy welds in Alloy 600, 625, 690, 800H, 825 and C-276 used in chemical and nuclear service
- Aluminum alloy fusion welds in 5052, 5083, 6061, 6082 and 7075 for marine, automotive and rail applications
- Titanium alloy welds in commercially pure Grades 1-2 and Ti-6Al-4V for aerospace and chemical plant equipment
- Copper and copper alloy welds in C11000, naval brass and aluminum bronze heat exchanger components
- Dissimilar metal welds between carbon steel and stainless steel, and between ferritic and austenitic steels
- Weld overlay and cladding, including 309L/308L stainless overlays and Inconel 625 cladding on steel substrates
- Spot welds, seam welds and projection welds in automotive body-in-white assemblies of mild and high-strength steels
- High-strength low-alloy steel welds (DP590, DP780, DP980, Q&P steels) with hot cracking and hydrogen cracking evaluation
- Friction stir welded joints in aluminum panels, tail-welded blanks and dissimilar aluminum-magnesium joints
- Laser beam welds and laser-hybrid welds in thin-gauge automotive and electronics components
- Electron beam welds in aerospace structures, gear assemblies and titanium pressure housings
- Flux-cored arc welds and self-shielded welds in structural fabrication and offshore platform nodes
- Gas tungsten arc welds in sanitary tubing, instrument lines and thin-wall stainless piping
- Electroslag and electrogas welds in thick-section box columns and heavy plate structures
- Stud welds, fillet welds and load-bearing attachments in steel building frames and bridge girders
- Repair welds and multiple-pass re-welds exhibiting reheat cracking, lamellar tearing or softening zones
- Galvanized and coated steel welds with liquid metal embrittlement (zinc-induced cracking) evaluation
- Cast iron weld repairs in grey iron HT200/HT250 and ductile iron QT450/QT500 components
- Welded tube-to-tubesheet joints in heat exchangers and shell-and-tube reactors
- Reinforcement bar splice welds and flash-butt welds in reinforced concrete structures
- Track welds in railway rails, including flash-butt and thermite (alumino-thermic) joints
- Soldered and brazed joint failure analysis in electronics, heat exchangers and copper assemblies
- Welded bellows, expansion joints and membrane panel welds in thermal power boiler water walls
weld failure analysis Application Scenarios
In thermal power generation, creep-resistant steel welds in Grade 91 main steam lines, boiler headers and water wall panels operate at 540-620 °C under internal pressure, and Type IV cracking in the intercritical HAZ is a recurrent failure mechanism. Weld failure analysis here centers on hardness traverses across the softened HAZ, replica metallography of creep cavities, carbide coarsening assessment by SEM, and cross-checking of post-weld heat treatment temperature records against observed microstructure. The analysis distinguishes premature Type IV failure from manufacturing defects such as lack of fusion, and informs remaining-life assessment and repair strategy.
In oil and gas pipeline construction, girth welds in X65 and X70 line pipe are examined when hydrostatic test failures or in-service leaks occur. The investigation typically addresses hydrogen-induced cold cracking in high-strength weld metal, incomplete root penetration in mechanized welding, solidification cracking associated with high sulfur or high phosphorus levels, and hook cracks near the bond line of ERW pipe. Fractography, metallography of the crack path relative to the fusion line, diffusible hydrogen measurement and carbon equivalent recalculation combine to determine whether the root cause lies in filler metal selection, welding parameters, preheat inadequacy or environmental exposure.
In shipbuilding, offshore structures and heavy steel fabrication, thick-section welds in EH36 and higher-grade plates are analyzed for lamellar tearing at T-joints, hydrogen cracking in highly restrained joints, and toughness degradation after multiple repair welds. The laboratory approach includes through-thickness tensile testing of the plate, inclusion morphology mapping, hardness profiling through successive weld passes, and Charpy testing of the coarse-grained HAZ. Findings guide changes to joint design, welding consumable choice, preheat and interpass temperature control, and the limitation of repair pass counts.
In automotive, rail and aerospace manufacturing, resistance spot welds in high-strength steels, laser welds in tailored blanks, and friction stir welds in aluminum closures are examined after static, fatigue or crash testing. The analysis addresses nugget diameter and fusion zone hardness, liquid metal embrittlement from zinc coatings, HAZ softening in press-hardened steels, porosity and keyhole instability in laser welds, and tunnel defects in friction stir welds. Fracture mode classification by SEM, cross-tension and peel testing correlation, and microstructural comparison between acceptable and failed welds allow the fabricator to lock in welding schedule parameters.
Summary
Weld failure analysis covers fracture surface examination, weld cross-section metallography, microhardness mapping, composition verification, hydrogen measurement, residual stress evaluation and mechanical property testing of failed welded joints in steels, stainless steels, aluminum, titanium and nickel alloys. The service addresses butt welds, girth welds, fillet welds, spot welds, laser and friction stir welds across pressure vessel, pipeline, power plant, shipbuilding, automotive and aerospace applications.
Standard turnaround is 7-15 working days depending on the selected test items and sample condition, with quotations issued by laboratory engineers based on the agreed testing plan.