Microstructure evolution in flow formed IN 718 products and subsequent fatigue crack growth properties

Abstract

With the drive towards cost‐effective routes for the manufacture of engineering components, flow forming technologies are now under consideration for the production of structural axisymmetric geometries such as tubes and cones. This near net shape process is known to offer improvements in material utilisation when compared with traditional processes where substantial final machining is required. The microstructure, evolved as a result of the flow forming process together with subsequent heat treatments, will govern associated mechanical properties. Laboratory measurements of the structure‐property relationships of flow formed material can be problematic, mainly because of the restrictions imposed on the extraction of conventional specimen geometries since most of the finished tubular or cone structures will contain thin and curved walls. The development of a suitable specimen design and associated test technique for the measurement of fatigue crack growth rates at room and elevated temperatures is presented. Data obtained from flow formed Inconel 718 (IN 718) will be compared with specimens of the exact same geometry but machined from conventionally forged IN 718 stock. This allowed for validation of the novel flow formed test in addition to an assessment of the damage tolerance of the flow formed variant. The intimate relationship between local microstructure and fracture mechanisms will be described.

Forming process and evaluation of chip in machining of high-strength steel by an independent-developed microgroove turning tool

“…According to the measurement results of chip thickness shown in Figure 6, with the growth of cutting velocity, the chip thickness reduces gradually. The smaller the chip thickness is, the smaller the counterforce is, and the smaller the strain is, and the more difficult the chip breaks according to equation (7). This illustrates that the analysis results are consistent with the previous.…”

“…Chiappini et al 5 investigated the stability in the cutting process completely neglecting the chip formation under variable spindle speed. Galatolo and Fanteria 6 and Bache et al 7 were concerned with the effect of cutting conditions on the fracture properties of workpiece materials to reveal the relationship between the fatigue crack growth and the chip formation. Yi et al 8 studied the effects of material response on the chip forming process in the processing of Inconel718, and found that the material responses of the tool-chip interface under cutting speeds are different.…”

Archives of Metallurgy and Materials

“…A g (I ) = -0.0727 • Z + 6.2331 (6) where: A g (I ) -elongation at maximum stretching force, Z -relative thickness reduction according equation (1). The use of heat treatment restores the plastic properties of the material.…”

“…Inconel 718 can be hardened by: cold working, age hardening, cold working followed by age hardening. As demonstrated in works [5,6], the forming method strongly influences the microstructure and precipitation process. The knowledge of the influence of cold plastic working parameters and heat treatment on the mechanical and plastic properties of this steel is particularly useful during the structural design of the given part and the technological design as well.…”

Statistical Analysis and Optimisation of Data for the Design and Evaluation of the Shear Spinning Process

“…Shear spinning is a method of rotating forming of components on a rotating forming block using a roller. This technique is recommended for small and medium series production of axisymmetric products [ 1 , 2 ]. Plastic deformation of the material in the process of shear spinning occurs by direct action of the pressing rollers on a small contact area with the material.…”