Tempering Influence on Residual Stresses and Mechanical Properties of AISI 4340 Steel

The present work evaluated the tempering temperature influence on microstructure, mechanical properties and residual stresses of AISI 4340 steel. The residual stresses were measured by X‑ray diffraction (XRD) by the sin²ψ method and compared to magnetic Barkhausen noise (MBN). The residual stresses exhibited high tensile values after quenching, but a small relief was observed in tempering treatments at 300°C and 400°C, which also presented a hardness decrease compared to the as‑quenched condition. XRD and MBN analyses indicated that residual stresses became compressive in tempering performed between 500°C and 650°C. Therefore, compressive residual stresses combined with appropriate hardness and toughness values (35 HRC and 33 J) obtained from 500°C tempering temperature can be used to improve the mechanical properties of AISI 4340 steel components. Additionally, a mathematical model was established to estimate the tempered martensite hardness for different tempering temperature conditions. This model showed high accuracy (R2=0.99) for a holding time of 90 minutes.

Evaluation The Performance Of Cvd And Pvd Coated Carbide Tool In Hard Turning Of Aisi-4340 Steel

The work introduced in this proposal tends to the surface unpleasantness and flank wear during hard turning of AISI 4340 steel (33HRC) utilizing CVD (TiCN/Spasm/Al2O3/TiN) multi-facet covered carbide device and PVD (TiCN/Al2O3) covered carbide device. Three variables (cutting rate, feed and profundity of cut) and three level factorial test plans with Taguchi’s L9OA and factual examination of difference were acted to explore the impact of these cutting boundaries on the apparatus and work piece as far as flank wear, and surface harshness. Additionally the examination of these impacts between previously mentioned sorts of apparatuses was finished. The outcomes show that for surface unpleasantness and flank wear, feed and cutting velocity were measurably huge and profundity of cut had least impact on both surface harshness and flank wear. For surface harshness, feed was more huge followed by cutting velocity for the two sorts of devices, while as, for flank wear cutting pace was more huge followed by feed for the two kinds of instruments. Surface completion was estimated in Ra boundary and a decent surface completion was acquired by PVD covered apparatus at low and medium rates, anyway with the speeding up the CVD covered carbide device showed better surface completion. Flank wear was estimated by utilizing optical magnifying instrument and the outcomes show that more wear happened in PVD covered carbide apparatus when contrasted with CVD covered carbide device under same cutting boundaries and natural conditions. Consequently for better surface completion at low and medium velocities PVD covered carbide apparatus is better and for higher paces, CVD covered carbide device is ideal. For low apparatus wear, CVD covered carbide device is liked.