M/S Toshiba JSW Turbine & Generator Pvt. Ltd. reported the failure of 10.7CrMoVNbN steel turbine blades used in its power plant for the production of electricity. The basic reason for its failure was the higher content of delta ferrite. The objective of the present study is to reduce the failure of 10.7CrMoVNbN steel caused by delta-ferrite inclusion. 10.7CrMoVNbN steel is used for the fabrication of steam turbine blades by M/S Toshiba JSW Turbine & Generator Pvt. Ltd. Four Heats with chemical composition as well as thermo-mechanical processing and heat treatment were prepared. The main variation in all Heats was the variation in \({\text{Cr}}_{\text{eq}}\). Samples were prepared as per standard metallographic technique. Samples etched with kalling’s-1 agent revealed a tempered martensite morphology. The morphology of tempered martensite got refined with the reduction in \({\text{Cr}}_{\text{eq}}\). Further, the samples when etched with sulfuric acid etchant revealed the delta-ferrite morphology. Delta ferrite decreased with a decrease in \({\text{Cr}}_{\text{eq}}\). FESEM-EDS analysis revealed the presence of carbides and various phases in the steel. Further, to confirm the presence of different phases in the steels, microhardness analysis was performed. Microhardness analysis revealed the presence of tempered martensite matrix, different carbides, and delta ferrite. Further, the decrease in \({\text{Cr}}_{\text{eq}}\) led to a marginal increase in yield strength, ultimate tensile strength, whereas a significant increase in impact strength was observed. Overall, Heat 4 with \({\text{Cr}}_{\text{eq}}\) of 11.59 showed the maximum improvement in the mechanical properties. Further, the δ-ferrite content of Heat 4 was 0.3% which was lower than the permissible limit of 2%. Hence, Heat 4 fulfilled the material specifications specified by Toshiba and reduced the material failure caused by δ-ferrite inclusions.

M / S东芝JSW涡轮和发电机列队。该公司报告了其发电厂用于发电的10.7CrMoVNbN钢制涡轮机叶片发生故障。其失败的根本原因是δ铁素体含量较高。本研究的目的是减少10.7CrMoVNbN钢由δ铁素体夹杂引起的失效。M / S Toshiba JSW Turbine＆Generator Pvt使用10.7CrMoVNbN钢制造蒸汽轮机叶片。制备了具有化学成分以及热机械加工和热处理的四个加热。所有加热的主要变化是\（{\ text {Cr}} _ {\ text {eq}} \）的变化。根据标准金相技术制备样品。用卡林氏-1试剂蚀刻的样品显示出回火的马氏体形态。减少\（{\ text {Cr}} _ {\ text {eq}} \）可以细化回火马氏体的形态。此外，当用硫酸蚀刻剂蚀刻时，样品显示出δ铁素体形态。δ铁素体随着\（{\ text {Cr}} _ {\ text {eq}} \}的减少而减少。FESEM-EDS分析表明钢中存在碳化物和各种相。此外，为了确认钢中存在不同相，进行了显微硬度分析。显微硬度分析表明存在回火马氏体基体，不同的碳化物和δ铁素体。此外，\（{\ text {Cr}} _ {\ text {eq}} \）的减少导致屈服强度和极限抗拉强度略有增加，而冲击强度则显着增加。总体而言，第4步的\（{\ text {Cr}} _ {\ text {eq}} \}显示出机械性能的最大提高。另外，热4的δ铁素体含量为0.3％，低于容许极限2％。因此，加热4满足了东芝规定的材料规格，并减少了由δ铁素体夹杂物引起的材料破坏。