Tribological Characteristics of Experimental Hard Alloy Grades With Modified Cobalt Binder Under Conditions of Dry Friction on Titanium-Aluminum Alloy Vt-3

Abstract

The paper is dedicated to investigations of tribological characteristics of experimental tool hard alloy (HA) grades based on tungsten carbide with modified cobalt binder under conditions of dry friction on disks made of titanium-aluminum alloy VT-3, as well as measures of their surface micro-hardness. All measured parameters were compared with similar characteristics of standard HA grade VK8, on the basis of which these experimental grades were developed. The research found that the surface micro-hardness of all experimental HA grades as pins were higher than that for the basic grade VK8; the highest value was fixed for the HA grade with symbol mark 2.22 (composition of the binder -5.65% Co +1.8% Mo +0.6% Ti). The highest wear resistance was obtained for 2.23 (5.1%Co+2.7%Mo+0.61%Ti) and 2.21 (5.4%Co+1.43%Fe+0.82% Cu), the lowest -for grade 2.22. The analysis of friction processes peculiarities allows to explain the high wear resistance of grades 2.21 and 2.23 by features of surface structures ("the third body") formation during friction. Friction process for these HA grades include the periods of "the third body" intensive growth to the considerable thickness values, as well as the periods of its abrasion; due to this phenomena resulting wear rates for these two grades proved to be significantly lower than for the base grade VK8. The "third body" generated during friction protects surfaces from wear, at the same time it has its own significant shear resistance and increases actual contact area, due to this phenomena the friction forces for grades 2.21 and 2.23 are somewhat higher than for basic grade VK8. The grade 2.22 is characterized by the highest average friction force and its r.m.s. deviation value, which result in the greatest wear rates for both the HA pins and rotating disks. So according to the results of testing the best results among the investigated experimental HA grades were obtained for grade 2.23: the lowest average friction coefficient and the lowest track surface roughness on rotating disks, as well as the highest wear resistance values.

Tribological properties of high-entropy high-speed steels under conditions of friction on stainless steel 12H18N9T

“…Thus, the process of frictional interaction with structural steel 30HGSA for these materials in similar tests is also characterized by the fastest increase in the thickness of the intermediate layer and the smallest change in the micro relief both on the surface of the indenter and on the friction tracks on the disk [14]. The process of friction of high-entropy experimental hard alloys on various structural materials proceeds according to a similar scenario [16,17]. The formation of a stable intermediate layer for this group of materials is facilitated, in particular, by their surface mechanical characteristics at the microlevel, i.e., higher values of microhardness and modulus of elasticity [13][14][15][16][17].…”

“…The process of friction of high-entropy experimental hard alloys on various structural materials proceeds according to a similar scenario [16,17]. The formation of a stable intermediate layer for this group of materials is facilitated, in particular, by their surface mechanical characteristics at the microlevel, i.e., higher values of microhardness and modulus of elasticity [13][14][15][16][17].…”

Thermodynamic foundations of the rational cutting modes choice under conditions of machining

“…High-entropy CTMs have a number of better physical, mechanical and tribotechnical characteristics in comparison with low-entropy materials. Such advantages include lower cutting forces and temperatures in the cutting zone, higher surface micro hardness and modulus of elasticity and better frictional characteristics [16]. The complex of such properties provides for these materials a general reduction in the wear intensity under various friction and cutting modes.…”

“…Durability tests also were carried out when turning work pieces of heat-resistant steel 12H18N10Т by tool inserts made of experimental single-carbide hard alloys with modified cobalt binder [14] created on the basis of the standard HA grade VK8 (Table 2). These HA grades are characterized by high thermal entropy values of the binder together with small values of absolute thermo-EMF which increases the electrochemical stability of these materials, and also characterized by an improvement in a number of operational and tribotechnical characteristics in comparison with the base composition [15,16]. Geometry parameters of the cutting part of the tool inserts: rake angle γ = 8˚, clearance angle α = 6˚, side cutting edge angle φ = 45˚.…”

Evaluation of tribo-vibration characteristics of the finishing turning process of heat-resistant structural steel 20MnMoNi5-5

“…Increasing the wear resistance of cutting tools is a very urgent problem, which is solved in various ways: by creating new tool materials with improved physical, mechanical and cutting properties [1][2][3][4], by modifying the working edges of the tool with wear-resistant coatings [5][6][7][8], by assessment of the thermal load of the tool [23] and by selecting optimal technological operating modes for the tool [9][10][11]. One of the main factors that contribute to the intensification of wear processes of tool cutting materials is significant vibrations in the cutting system.…”