No abstract

The study analyzes physicomechanical and thermophysical properties of hard alloys with due regard to their chemical composition; reveals the dependence of both the cutting properties and regularities of carbide tool wear from cutting conditions and thermophysical properties of tool material; describes a significant impact of not only mechanical but, first and foremost, thermophysical properties of instrumental and structural materials on tool wear; and identifies ways to reduce the wear rate of a cutting tool.

Abstract. The analysis of physic-mechanical and thermal physic properties of hard alloys depending on their chemical composition is conducted. The correlation of cutting properties and regularities of carbide tool wear with cutting conditions and thermal physic properties of tool material are disclosed. Significant influence on the tool wear of not only mechanical, but, in the first place, thermal physic properties of tool and structural materials is established by the researches of Russian scientists, because in the range of industrial used cutting speeds the cause of tool wear are diffusion processes. The directions of intensity decreasing of tool wear by determining rational processing conditions, the choice of tool materials and wear-resistant coating on tool surface are defined. Analysis of the mechanism of carbide tool wearDepending on the physical-mechanical properties of work and tool materials, the type of contact interaction, contact temperatures and contact stresses, the type of lubricant-cooling agents, their cooling effect, the possibility of lubricant-cooling agents penetration on the boundary surface of contact interaction and of chemical reactions passing there, as well as the possibility of diffusion processes passing through the boundary of work and tool materials, tool wear can have various physical nature and there may be various wear mechanisms.The diversity of wear content and manifestations can be divided into two types: continuous dissolution at atomic level of worn material in the wearing; wear by removing discrete submicro-and micro-volumes from worn surface, having finite geometrical dimensions.While cutting metals can take place following wear mechanisms: diffusion, adhesion-fatigue, oxidation, abrasive and wear as a result of cutting edge microspall [13]. The diffusion wear is most common of them, which can be described in the following way. Mutual diffusion of tool and work materials occurs while cutting in determination conditions of stable adhesion bond. During this process takes place, first, the carbides dissociation (mostly tungsten carbides) and subsequent diffusion of the elements (W, Ti, C) in the work material (direct diffusion dissolution); second, metal elements diffusion of the work material in the binding phase of hard alloy and its softening. The consequence is bond weakening, holding carbide grains or groups of carbides in the hard alloy, tear-out and ablation by their border volumes of work material. The result of both processes is the wear of tool contact surfaces.According to the views of N. V. Talantov [14], the type of contact interaction in a certain way has an influence on the mechanism and intensity of tool wear, as well as forming main characteristics of the cutting process. It is known that while cutting carbon and lowalloy ferrite-pearlite steels with increase in cutting speed there is regular change of the following types of contact interaction: build-up, throbbing contact zone, and zone of relative stagnation, plastic and viscous contact. For high-alloy s...

The paper provides the results of experimental studies of changes in the depth of the defective layer during milling of various structural materials; shows the convergence of the experimental results with the data published in open-access publishing; substantiates a logical change in the depth of the defective layer at various stages of multi-stage machining; and builds probabilistic tables of milling accuracy.

Abstract.A mechanisms of wear carbide tool when turning of austenitic steel 18-8 by cutters from firm hard-alloys of various groups (WC-Co, TiC-WC-Co, TiC-TaC-WC-Co) were studied. During wear resistant tests it is established, that the prevalence of one of the two mechanisms of wear (of adhesion-fatigue or diffusional) depends on the brand of hard alloy. It is shown, that in machining by titanium-containing carbide tool the intensity of the growth of the wear platform on the back surface of the tool as wear changes. This is due to the smooth transition from the predominance of adhesion-fatigue wear to prevalence of diffusional wear. Therefore, the intensity of wear should be considered as current, depending on the value wear platform, and value of the criterion of blunting is influence on the selection of the brand of hard-alloy and optimum cutting speed.In theory and practice of cutting of metals much attention is pay to the selection of the most effective brand of hard alloy and to definition of optimal cutting speed. The urgency of this problem increases in the case of cutting of austenitic steels and other materials that are hard to machining.The appointment of a hard alloy is produced mainly on the basis of the machined material and the type of machining (the machining type is qualitatively to fix -roughing, semi-finishing and finishing). Optimum cutting speed, i.e. the speed corresponding to the maximum path length of cut up to a specified criterion blunting (permissible value wear) tool, is considered as a fixed, unchanging from the beginning of cutting to blunting the tool under given conditions (machined and tool materials, modes of cutting, tool geometry, and so on).It has been established that a wide range of cutting speeds in machining austenitic steel at the wear platform at the rear surface of tool prevails plastic contact -complete adhesion of the machining material to the tool, with plastic flow of the machined material [1]. However, adhesive-fatigue wear is retained to high cutting speeds and hence high temperatures at the wear platform, -especially for tools made of titanium-containing hard-alloys of TiCWc-Co and TiC-TaC-WC-Co. This is associated with the unstable chip formation seen in cutting austenitic steel, which leads to cyclic fluctuation of the forces and thermal loads on the wear area of the tool's rear surface [2,3]. It influence on the peculiarities of tool wear. It is important to establish this peculiarities.The endurance-tests carried out by the longitudinal turning austenitic steel 18-10 (Fe and C ≤ 0,12 %, Cr 18 %, Ni 10 %, Ti ≤ 0,8 %), showed that when choosing a brand of hard alloy and value of optimal cutting speed should take into account the criterion of blunting the tool (in most cases -allowable width hre of the wear platform on the rear surface).In our experiments we used cutters with mechanically fixed plates of various hard alloys -WC 94-Co 6, TiC 15-WC 79-Co 6 and TiC 8-TaC 12-WC 71-Co 9. The speed v of cutting was changed from 15 to 180 m/min at supply 0.3 mm/turn an...