Search Results for quantitative acoustic emission method

High-pressure and high-temperature piping in fossil power plants suffer from unexpected and rarely predictable failures. To prevent failures and ensure operational safety, a Quantitative Acoustic Emission (QAE) non-destructive inspection (NDI) method was developed for revealing, identifying, and assessing flaws in equipment operating under strong background noise. This method enables overall piping inspection during normal operation, locating suspected zones with developing low J-integral flaws, identifying flaw types and evaluating danger levels based on J-integral values, and detecting defective components prior to shutdown. Combining continuous and burst acoustic emission as an information tool, the QAE NDI revealed, identified, and assessed significant flaws like creep, micro-cracks, pore/inclusion systems, plastic deformation, and micro-cracking in over 50 operating high-energy piping systems. Findings were independently verified by various NDI techniques, including time of flight diffraction, focused array transducers, magnetic particles, ultrasonic testing, X-ray, replication, and metallurgical investigations.

Theoretical and experimental investigations, including fracture tests, acoustic emission (AE) studies, fractography, micro-sclerometric analyses, and spectral/chemical analyses of specimens, have established the possibility of revealing, recognizing in-service acquired, age-related, and prefabricated flaws based solely on AE data. Results show a linear dependence between AE and mechanical deformation power of steel specimens in original and creep stage 3a-3b conditions, decreasing fracture load and J1c value for aging steel, creep processes at stage 3a-3b having J-integral value below 0.05J1c, possibility of assessing and distinguishing different flaw development stages with ≥87% accuracy, revealing zones of tough and brittle fracture, and recognizing inclusions/pre-fabricated flaws and assessing individual/interacting flaws. Experiments confirmed the absence of the Kaiser effect under repeated loading of flawed specimens and demonstrated using AE for defect revelation. Analysis showed that creep-associated AE is mainly continuous, with repeated loading decreasing burst AE contribution during plastic deformation development.

Both non-destructive and traditional microsectioning techniques have been used to measure the oxide thickness of steam grown oxides between two close contacting surfaces. Different power plant materials, nickel based alloys and ferritic-martensitic steels, were exposed to steam oxidation at temperatures ranging from 650 °C up to 750 °C and periods from 500 h to 3000 h. Ultrasonic measurements of thickness, based on the speed of sound in the oxide, were performed and compared to optical thickness measurements based on conventional metallographic microsectioning with promising results. Improvements on the measurement resolution have been practically demonstrated with oxides down to 65 μm thickness being measured successfully.

Solid particle erosion (SPE) and liquid droplet erosion (LDE) cause severe damage to turbine components and lead to premature failures, business loss and rapier costs to power plant owners and operators. Under a program funded by the Electric Power Research Institute (EPRI), nano­coatings are under development for application in steam and gas turbines to mitigate the adverse effects of PE and LPE on rotating blades and stationary vanes. Based on a thorough study of the available information, most promising coatings such as nano-structured titanium silicon carbo-nitride (TiSiCN), titanium nitride (TiN) and multilayered nano coatings were selected. TurboMet International (TurboMet) teamed with Southwest Research Institute (SwRI) with state-of-the-art nano-technology coating facilities with plasma enhanced magnetron sputtering (PEMS) method to apply these coatings on various substrates. Ti-6V-4Al, 12Cr, 17-4PH, and Custom 450 stainless steel substrates were selected based on the current alloys used in gas turbine compressors and steam turbine blades and vanes. Coatings with up to 30 micron thickness have been deposited on small test coupons. These are extremely hard coatings with good adhesion strength and optimum toughness. Tests conducted on coated coupons by solid particle erosion (SPE) and liquid droplet erosion (LDE) testing indicate that these coatings have excellent erosion resistance. The erosion resistance under both SPE and LDE test conditions showed the nano-structured coatings have high erosion resistance compared to other commercially produced erosion resistance coatings. Tension and high-cycle fatigue test results revealed that the hard nano-coatings do not have any adverse effects on these properties but may provide positive contribution.

Erosion from solid and liquid particles in gas turbine and steam turbine compressors degrades efficiency, increasing downtime and operating costs. Conventional erosion-resistant coatings have temperature and durability limitations. Under an Electric Power Research Institute (EPRI) project, ultra-hard nano-coatings (~40 microns thick) were developed using Plasma Enhanced Magnetron Sputtering (PEMS). In Phase I, various coatings—including TiSiCN nanocomposites, stellite variants, TiN monolayers, and multi-layered Ti-TiN and Ti-TiSiCN—were deposited on turbine alloys (Ti-6Al-4V, 17-4 PH, Custom-450, and Type 403 stainless steel) for screening. Unlike conventional deposition methods (APS, LPPS, CVD, PVD), PEMS employs high-current-density plasma and heavy ion bombardment for superior adhesion and microstructure density. A novel approach using trimethylsilane gas successfully produced TiSiCN nanocomposites. Stellite coatings showed no erosion improvement and were discontinued, but other hard coatings demonstrated exceptional erosion resistance—up to 25 times better than uncoated substrates and 20 times better than traditional nitride coatings. This paper details the deposition process, coating properties, adhesion tests, and characterization via SEM-EDS, XRD, nanoindentation, and sand erosion tests.