THE
INFLUENCE OF MICROSTRUCTURE AND HYDROGEN-CONTAINING ENVIRONMENT ON THE
INTENSITY OF CAST IRON AND STEEL DAMAGE BY SLIDING FRICTION
PART 1. THE CONSTRUCTION OF A
GENERALIZED MODEL OF SURFACE LAYER FRICTION OF GRAPHITIZED STEEL AND CAST-IRON OBJECTS
PART 1
PART 1, PART 2, PART 3, PART 4, PART 5, PART 6, PART 7
Keywords
Microstructure, hydrogen, sliding friction,
graphitized steel, cast iron
Abstract
This paper analyzes mechanisms of abrasive wear
on the basis on the research results and literary data. A generalized model
describes the influence of microstructure, chemical composition and hydrogen-containing
lubricant on the wear processes in the surface layers of cast irons and
graphitized steels. Major factors affecting the intensity of wear are
determined: pressure, speed of sliding,
chemical composition and microstructure.
Introduction
The microstructure of Fe – C alloys during
friction (dry friction in particular) plays a key role in the intensity of
abrasive wear. Cast iron is one of the most widely used constructional
tribo-technical materials. However, these alloys are fairly complex in terms of
the variety and quantity of structural and phase components. The formation of
cast-iron microstructure is influenced by a great amount of controllable and
uncontrollable factors [1 - 3]. Graphitized steel is quite similar to
investigated alloys due to its microstructure and properties. Therefore, many
statements in this publication relate to graphitized alloys as well [4,5].
Nevertheless, despite obvious progress in the creation of new structural
materials (nanomaterials, composite materials, high-strength steels), cast-iron
and low alloyed steels will continue to be used as structural materials for the
next several decades [5, 6]. First of all, they will be used for reconditioning
of worn machine components to extend
their service life.
In many cases the normal mode of friction
depends on the durability of contacting surfaces (including hydrogen-containing
cooling environments). One way of increasing the durability of cast-iron and
steel is by additional alloying. Interaction occurs at points of contact. Their
sizes, distribution, migration time and speed of occurrence are not completely
known; however, according to some information, the total time of their
existence is 10-3 - 10-5 seconds [7]. It is obvious that
the interactions at points of contact depend on various, mainly physical and
chemical, properties of structural and phase elements contained in Fe - C
alloys. However, this problem has not been completely studied yet.
Results
and discussion
There are a lot of models for nearly solid body
layer structures and surfaces of friction [8 - 10]. Let us consider some of
them (Fig. 1.).
There are also some more complex
classifications of superficial and under surface layers structure, such as the
one offered by Burakowski [11] (Fig. 2.).
The microstructure considered in Fig. 1 can
reflect the condition of retaining ring steel microstructure [12, 13], e.g.,
containing up to 21 % Mn, and some kinds of steel that has a structure a little bit simpler than that in
cast-alloys. It should be noted, however,
that their behavior during sliding friction has not been studied
completely [14, 15].
A large supply of
techniques for enhancing tribotechnical properties of both steels and cast-irons is the improvement of
their microstructure by metallurgical methods (alloying, modifying), as well as
heat treatment, chemical and thermal processing, laser processing, etc., or
finally, by using new lubricating materials, which minimize or even completely
prevent deterioration.
PART 2
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