Influence of cutting parameters and tool wear on the surface integrity of cobalt-based Stellite 6 alloy when machined under a dry cutting environment

The efficiency of a machining process can be measured by evaluating the quality of the machined surface and the tool wear rate. The research reported herein is mainly focused on the effect of cutting parameters and tool wear on the machined surface defects, surface roughness, deformation layer and residual stresses when dry milling Stellite 6, deposited by overlay on a carbon steel surface. The results showed that under the selected cutting conditions, abrasion, diffusion, peeling, chipping and breakage were the main tool wear mechanisms presented. Also the feed rate was the primary factor affecting the tool wear with an influence of 83%. With regard to the influence of cutting parameters on the surface roughness, the primary factors were feed rate and cutting speed with 57 and 38%, respectively. In addition, in general, as tool wear increased, the surface roughness increased and the deformation layer was found to be influenced more by the cutting parameters rather than the tool wear. Compressive residual stresses were observed in the un-machined surface, and when machining longer than 5 min, residual stress changed 100% from compression to tension. Finally, results showed that micro-crack initiation was the main mechanism for chip formation

Impact du revêtement sur le comportement à l’usure et sur la rugosité de la surface usinée en fraisage frontal de l’acier C18

Cette étude est basée sur une analyse expérimentale des performances de coupe de plaquettes de fraisage en carbure métallique ISO P35. La première série est non revêtue et l’autre revêtue avec une simple couche de (TiN). Les essais sont réalisés en fraisage à l’aide d’une fraise à surfacer de type tourteau à huit dents lors de l’usinage de l’acier ISO C18. L’objectif est le suivi, d’une part de l’évolution de l’usure en dépouille de ces plaquettes en fonction du temps, et d’autre part de la rugosité en fonction des conditions de coupe et de l’usure. Les résultats expérimentaux obtenus permettent d’établir des modèles mathématiques exprimant la relation qualitative et quantitative entre les éléments du régime de coupe et les paramètres technologiques exprimés par la durée de vie (T) et la rugosité arithmétique de la surface usinée (Ra). L’analyse des résultats a fait ressortir que les plaquettes revêtues sont de trois à quatre fois plus performantes. Ce qui permet également d'obtenir des surfaces usinées de meilleure qualité. En effet, la valeur de Ra est réduite de moitié pour les régimes à grandes vitesses de coupes et faibles avances.Mots clés: Fraisage; carbures métalliques; revêtements d’outils; usure; acier ISO C18; Rugosité. This study is based on an experimental analysis of cutting performances for two nuances of metallic carbides. The first carbide insert is uncoated and the second is coated with one layer of (TiN). The tests are realized under face milling of ISO C18 steel using a surfacing cutter with eight teeth. The objective of this study is to follow the evolution of tool wear according to time and to assess roughness according to both cutting conditions and wear rates. The results allowed establishing mathematical models relating the work conditions and the technological parameters such as tool life and machined surface roughness (Ra). Analysis of the results showed that the coating inserts have 3 to 4 times better performance in terms of tool life in comparison with the uncoated ones. In terms of surface quality, the value of the absolute roughness is reduced by half under high cutting speeds and small feed rates per tooth.Keywords: Face milling; metallic carbides; tool coatings, wear; steel C18; roughness

Dry high speed milling of nickel-based superalloy

International audienceInconel 718 Nickel-based superalloy has been applied widely in high temperature, high load and corrosion resistant environments due to its superior properties. They are known to be among the most difficult-to-cut materials. This paper reports some experimentals findings concerning the machinability at high cutting speed in milling process. To characterize the machining of Inconel 718 by tips tools, to identify the best cutting conditions, to define the modes of wear, to determine the tool life, and to classify the types of coatings. The study is conducted according to two phases. Phase one, determination of the cutting conditions for a comparative study. Machining over some lengths with selected tips in order to determine the strategy of milling. Phase two, Study of the types of wear. During machining, the modes of wears are observed and the powers of cut are raised and referred. High speed milling machine equipped by a power consumption recorder Wattpilote. The aim is to show the machinability of the superalloy, measuring the power and the tip wear by optical microscope and white light interferometer, using different strategies and cutting conditions

Machinability of Stellite 6 hardfacing

This paper reports some experimental findings concerning the machinability at high cutting speed of nickel-base weld-deposited hardfacings for the manufacture of hot tooling. The forging work involves extreme impacts, forces, stresses and temperatures. Thus, mould dies must be extremely resistant. The aim of the project is to create a rapid prototyping process answering to forging conditions integrating a Stellite 6 hardfacing deposed PTA process. This study talks about the dry machining of the hardfacing, using a two tips machining tool and a high speed milling machine equipped by a power consumption recorder Wattpilote. The aim is to show the machinability of the hardfacing, measuring the power and the tip wear by optical microscope and white light interferometer, using different strategies and cutting conditions

Machinability of Stellite 6 hardfacing

This paper reports some experimental findings concerning the machinability at high cutting speed of nickel-base weld-deposited hardfacings for the manufacture of hot tooling. The forging work involves extreme impacts, forces, stresses and temperatures. Thus, mould dies must be extremely resistant. The aim of the project is to create a rapid prototyping process answering to forging conditions integrating a Stellite 6 hardfacing deposed PTA process. This study talks about the dry machining of the hardfacing, using a two tips machining tool and a high speed milling machine equipped by a power consumption recorder Wattpilote. The aim is to show the machinability of the hardfacing, measuring the power and the tip wear by optical microscope and white light interferometer, using different strategies and cutting conditions