Influence of the microstructure of cast iron on the rheological properties of frictional contact and wear-resistance a*

Abstract The influence of sliding speed and contact load on wear-resistance of cast iron in the unhardened state (cast without heat treatment) and in the state after surface hardening by electroarc plasma (GTAW method) is investigated. This method provides formation of composite hardening structure in the process of fast crystallization. It is shown, that during friction of hardened cast iron the contribution of mechanical-thermal hardening with simultaneous development of relaxation processes prevails over mechanical peening. It provides high level and stability of wear-resistanc

Effect of the Viscoelastic Properties of Treated Steel on the Rheology and Dissipative Properties of Frictional Contact

Effect of the tempering temperature of hardened carbon steel and conformable structural changes on physical-mechanical properties and tribological characteristics during dry sliding friction was researched. It is shown, that relation between adhesive and deformational components of the frictional force depends on acquired during tempering viscoelastic properties that influence on mechanism of the contact interaction and dissipative processes. Viscoelastic properties are detected by two basic rheological parameters: modulus of elasticity and damping capacity, with which the viscoelastic coefficient is connected. The theoretical analysis of dissipative properties of the viscoelastic frictional contact dissected subject to the structure of tempered steel on the base of examined standard rheological models

Dynamic Processes of Substructural Rearrangement under Friction of Carbon Steel

The effect of heat treatment (tempering temperature after quenching) of medium carbon steels (steel 45 and steel 50) on tribological indicators at sliding friction without lubrication in connection with the change in strength and rheological elastic properties of steel, controlling the dissipative properties of the frictional contact has been studied. Tribotechnical tests were conducted according to two schemes. A high-temperature tribometer was used for “soft” friction according to the “ball-plane” scheme, which allowed varying the temperature of the friction contact. Influence of load-rate modes was studied in more “hard” conditions on the friction machine under the “finger-disk” scheme. Substructural transformations of steel caused by heat treatment were evaluated by changes in amplitude-dependent internal friction on a torsion pendulum-type machine, which also allowed measuring frictional damping (contact internal friction) in the preliminary displacement mode. The interrelation between hardness, elastic modulus and internal friction of steel and wear resistance, wear capacity, friction coefficient and the level of frictional damping has been established. It is shown that the growth of elastic modulus and increase of steel relaxation resistance after the appropriate heat treatment are conjugated with the development of adhesion and setting, which, as topochemical reactions in the solid phase, are the leading forms of contact stress relaxation under the above conditions. Correlation of tribological indicators of external friction with amplitude-dependent and relaxation (temperature-dependent) internal friction taking into account structural state of steel and friction temperature regime is established. Substructural preconditions, dynamic relaxation mechanisms of hardening and load-temperature friction conditions under which martensitic structures exhibit abnormally high wear resistance and significant growth of frictional damping level are considered. The tribological analogue of the Porteuen - Le Chatelier effect, manifesting in the form of frictional self-oscillations in the range of temperatures of dynamic deformation aging is established. A treatment of the nature of the Kael-Ziebel effect, the temperature-rate and load localization of which in friction is associated with the temperature range of dynamic strain aging with Snook-Kester relaxation superimposed, is propose