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2848 |
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Tuesday, September 27, 2011, Saal B2.1 2:00 PM Cold Spraying 1 |
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Study of powder condition influence on precipitation hardening stainless steel coatings obtained with cold gas spraying |
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Sergi Dosta / Thermal Spray Centre (CPT) - Universitat de Barcelona, SPAIN Carlos Lorenzana* / CPT Thermal Spray Centre, Spain Nuria MartÃnez/ CPT Thermal Spray Centre, Spain S. Dosta/ CPT Thermal Spray Centre, Spain J. Guilemany/ CPT Thermal Spray Centre, Spain |
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Cold Gas Spray allows to extend the range of steel formulations from which a coating can be obtained in comparison with other thermal spraying techniques because the material doesnt melt during process. In addition, the absence of processes of fast solidification implies the absence of tensile stresses in the coating and makes possible to obtain thick coatings. These coatings constitute a new alternative to welding cladding processes for the restoration of surfaces with corrosion pitting, notched areas or welded zones with bad appearance and for the repair of porous casting, contractions or losses of tolerance, by applying located coatings. 17-4 PH steel is one of the most widely used precipitation hardening grades in the business, offering high strength with corrosion resistance similar to type 304 in most environments. While soft and ductile in the solution annealed condition, it is capable of high properties with a single precipitation or aging treatment. Characterized by good corrosion resistance, high harness, toughness and strength. Commonly used in both aircraft and gas turbines, nuclear reactor, paper mill, oil field, and chemical process components. A study has carried out in Thermal Spray Center for the obtention and optimization of thick coatings of 17-4 PH steel through Cold Gas Spray technology (equipment CGT KINETICS 4000) onto carbon steel substrates. The study concentrates in the determination of influence of powder condition (heat treatment) on coating properties. For each condition, powder characterization includes measurement of particle size and morphology and phase distribution through a complete microstructural characterization including optical and scanning electronic microscopy. Each condition is then sprayed following a experiment desing of 3 variables and 2 levels. Thickness, hardness and porosity are measured for every sample and complete microstructural characterization of coating in cross section is done. The results show a great influence of the condition of 17-4 PH steel powder in the properties of the coating and the process economy. |