Titanium and nickel alloys represent a significant metal portion of the aircraft structural and engine components. When these critical structural components in aerospace industry are manufactured with the objective to reach high reliability levels, surface integrity is one of the most relevant parameters used for evaluating the quality of finish machined surfaces. The residual stresses and surface alteration (white etch layer and depth of work hardening) induced by machining of titanium alloys and nickel-based alloys are very critical due to safety and sustainability concerns. This review paper provides an overview of machining induced surface integrity in titanium and nickel alloys. There are many different types of surface integrity problems reported in literature, and among these, residual stresses, white layer and work hardening layers, as well as microstructural alterations can be studied in order to improve surface qualities of end products. Many parameters affect the surface quality of workpieces, and cutting speed, feed rate, depth of cut, tool geometry and preparation, tool wear, and workpiece properties are among the most important ones worth to investigate. Experimental and empirical studies as well as analytical and Finite Element modeling based approaches are offered in order to better understand machining induced surface integrity. In the current state-of-the-art however, a comprehensive and systematic modeling approach based on the process physics and applicable to the industrial processes is still missing. It is concluded that further modeling studies are needed to create predictive physics-based models that is in good agreement with reliable experiments, while explaining the effects of many parameters, for machining of titanium alloys and nickel-based alloys.

Machining induced surface integrity in titanium and nickel alloys: A review

Recent advances in modelling of metal machining processes

Nickel-based superalloy is widely employed in aircraft engines and the hot end components of various types of gas turbines with its high strength, strong corrosion resistance and excellent thermal fatigue properties and thermal stability. However, nickel-based superalloy is one of the extremely difficult-to-cut materials. During the machining process, the interaction between the tool and the workpiece causes the severe plastic deformation in the local area of workpiece, and the intense friction at the tool–workpiece interface. The resulting cutting heat coupled with the serious work hardening leads to a series of flaws, such as excessive tool wear, frequent tool change, short tool life, low productivity, and large amount of power consumption etc., in which the excessive tool wear has become one of the main bottlenecks that constraints the machinability of nickel-based superalloys and its wide range of applications. In this article, attention is mainly focused on the tool wear characteristics in the machining of nickel-based superalloys, and the state of the art in the fields of failure mechanism, monitoring and prediction, and control of tool wear are reviewed. The survey of existing works has revealed several gaps in the aspects of tool self-organizing process based on the non-equilibrium thermodynamics, tool wear considering the tool nose radius, thermal diffusion layer in coated tools, tool life prediction based on the thermal–mechanical coupling, and industrial application of tool wear online monitoring devices. The review aims at providing an insight into the tool wear characteristics in the machining of nickel-based superalloys and shows the great potential for further investigations and innovation in the field of tool wear.

Tool wear characteristics in machining of nickel-based superalloys

Size effects in manufacturing of metallic components

Chatter vibrations are present in almost all cutting operations and they are major obstacles in achieving desired productivity. Regenerative chatter is the most detrimental to any process as it creates excessive vibration between the tool and the workpiece, resulting in a poor surface finish, high-pitch noise and accelerated tool wear which in turn reduces machine tool life, reliability and safety of the machining operation. There are various techniques proposed by several researchers to predict and detect chatter where the objective is to avoid chatter occurrence in the cutting process in order to obtain better surface finish of the product, higher productivity and tool life. In this paper, some of the chatter stability prediction, chatter detection and chatter control techniques for the turning process are reviewed to summarize the status of current research in this field. The objective of this review work is to compare different chatter stability prediction, chatter detection and chatter control techniques to find out most suitable technique/s and to identify a research scope in this area. One scope of research has been identified as establishing a theoretical relationship between chatter vibration and tool wear in order to predict tool wear and tool life in the presence of chatter vibration.

A review of chatter vibration research in turning

Finite element modeling of residual stresses in machining induced by cutting using a tool with finite edge radius

Progressive tool-wear mechanisms and their effects on chip-curl/chip-form in machining with grooved tools: an extended application of the equivalent toolface (ET) model

Machining stability in turning operation when cutting with a progressively worn tool insert

The objective of this paper is to study void evolution and its effects on material failure during the machining process. The influence of cutting conditions on void nucleation, growth and coalescence is studied. The ultimate goal of this approach, as applied to machining, is to predict chip breakage and surface conditions via damage mechanics. A damage mechanics model proposed by Komori [1] is chosen to study the evolution of the void volume fraction in the chip and workpiece being machined with a grooved tool. A Thomason [2] type criterion as modified by Dhar et al. [3], that uses the variables calculated by FEM analysis, is used to predict void coalescence (failure). The distribution of the variables, such as effective strain-rate, nondimensional hydrostatic stress, and effective strain are obtained using the FEM methodology described by Zhang [4]. It is found that void coalescence always occurs in the newly machined surface below the flank face of the tool and in the chip flowing around the chip-groove region near the upper end of the face land. On the other hand, whether void coalescence occurs inside the chip or not, depends on the complex interactions between the machining parameters and chip geometry.© 2002 ASME

K.C. Ee

Papers

Finite element modeling of residual stresses in machining induced by cutting using a tool with finite edge radius

Progressive tool-wear mechanisms and their effects on chip-curl/chip-form in machining with grooved tools: an extended application of the equivalent toolface (ET) model

Machining stability in turning operation when cutting with a progressively worn tool insert

A Finite Element Analysis of Void Evolution in 2-D Machining