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FV520B不銹鋼激光熔覆熱影響區組織演變及其對力學性能的影響
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更新時間：2015-11-02
對FV520B不銹鋼零件的激光熔覆熱影響區進行了組織特征分析，結合過冷奧氏體連續冷卻轉變（CCT）實驗、模擬熱影響區拉伸及沖擊實驗，研究了熱影響區組織及力學性能的演變規律和機理。
FV520B不銹鋼激光熔覆熱影響區組織演變及其對力學性能的影響HEAT-AFFECTED ZONE MICROSTRUCTURE EVOLUTION AND ITS?EFFECTS ON MECHANICAL PROPERTES FOR LASER CLADDING?FV520B STAINLESS STEEL
對FV520B不銹鋼零件的激光熔覆熱影響區進行了組織特征分析，結合過冷奧氏體連續冷卻轉變（CCT）實驗、模擬熱影響區拉伸及沖擊實驗，研究了熱影響區組織及力學性能的演變規律和機理。結果表明：熱影響區可以按照組織演化特點分為4個特征區域，半熔區(A區)、析出相溶解區(B區)，完全奧氏體化區(C區)，部分奧氏體化區(D區)。各區域均為馬氏體組織，靠近界面區域的組織較為粗大，第二相發生溶解，硬度更高，固態相變點更低；距界面稍遠區域回火馬氏體增多，第二相未溶解，但有長大的趨勢，硬度較低，固態相變點較高，接近原始材料。決定激光熔覆熱影響區組織及力學性能的最主要因素是熱循環的最高溫度，最高溫度越高，強度損失越大，固態相變點越低，相應硬度越高，延伸率及沖擊功降低。?
FV520B steel is a martensitic stainless steel developed by Firth-Vickers. With its good corrosion?resistance and weldability, high strength and toughness. It has been widely used in heavy load and?corrosion-resistant components such as compressor impeller, valves, fasteners and pump shafts, which are easy to?be damaged because of severe service-environments. The production cycle of those expensive components are?long. If we can repair and remanufacture these components, the accessional value of the products can be reserved.?At the same time, it can save time, resources and funds, and reduce environmental pollutions. Laser cladding is an?attractive green reconstruction technology, which is widely used for the remanufacturing of faulty metal parts.?However, the heat-affected zone (HAZ) of remanufactured parts will experience cycles of heating and cooling?during the cladding operation, its properties will change and may be extremely different than that of the unaffected?area of the base material. Hence, the study of HAZ of FV520B steel is essential.?
The laser cladding on FV520B stainless steel was conducted to investigate the microstructure and mechanical?property development of HAZ. The microstructure of the HAZ was characterized by means of OM and SEM, and?hardness distribution was measured. Thermo-simulation was carried out to analyze the continuous cooling?transformation (CCT) diagram, which provides useful instructions to investigate the microstructure evolution of?HAZ. Simulated HAZ specimens and its mechanical properties were obtained by Gleeble3500?thermal/mechanical simulator and MTS810 material testing system. The results indicate that, microstructures of?the HAZ are martensite, the grain grows and second phase particles dissolve in the areas near the fusion zone.?Meanwhile, its martensite start temperature lower, and hardness higher than that of the unaffected area of the base?material. The maximum temperature of thermal cycle dominates the evolution of microstructure and property of?HAZ. With the decrease of the maximum temperature, the solid-state transformation temperature, elongation and?impact energy higher, and the hardness decrease. Thermal cycle have a little influence to the tensile strength of?HAZ under the processing parameters in this study. It can be speculated that the reduction in impact toughness?and elongation of the HAZ can be controlled by decreasing the scanning speed of cladding.
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