Modern industry requires use of materials with such properties
as, high hardness, fatigue strength, wear and corrosion resistance.
Surface engineering, especially recently developed hybrid technologies,
which involve the use of two or more surface treatments,
allow to meet these requirements. These processes result in manufacturing
of composite layers with new, improved and complementary
properties when compared to layers produced in separate
In this study hybrid method consists of plasma nitriding and
electroless nickel plating. Plasma nitriding of steel processes allow
producing nitrided layers of specified structure [2, 3], guaranteeing
increase in hardness, wear resistance and fatigue strength [1÷5].
Meanwhile, electroless nickel plating, which is widely used in industry,
enables the production of coatings characterized by high
corrosion resistance. Subsequent heat treatment of the Ni(P) coating
leads to its increased hardness and wear resistance [6, 7].
Production of composite layers consisting of nitrided layer and
Ni(P) coating requires good adhesion of the coating to the nitrided
substrate. In the study, the influence of nitrided layers’ structure
(phase composition) and surface topography on adhesion of Ni(P)
coating was investigated.
The study includes results of tests on surfaces roughness, composite
layers microstructure, as well as their hardness and adhesion.
2. EXPERIMENTAL PROCEDURE
The material examined in the experiments was 1.2343 (WCL) steel
with following chemical composition (mass %): C - 0.32÷0.42%,
Cr - 4.5÷5.5%, Mn - 0.2÷0.6%, Si - 0.8÷1.2%, Mo - 1.2÷1.5%,
V - 0.3÷0.5%, Fe - balance, hardened and tempered to hardness of
49 HRC. Specimens sized at Ø40×4.3 mm were subjected to glow
discharge nitriding in the mixture of N2 and H2 (1:1) at a temperature
of 530°C and a pressure of 2.5 hPa for 6 h. Then, part of the
samples were grinded on #220 or #800 abrasive pap więcej »
AISI316L stainless steel is a commonly used corrosion-resistant
and heat resistant material. Single phase austenitic microstructure
as well as an effective balance of carbon, chromium, nickel and
molybdenum content is a reason for such advantageous properties.
Therefore, this steel is often used wherever a high temperature
or aggressive corrosive media occur. 316L steel is also characterized
by paramagnetic properties, a substantial ductility, low yield
strength, high ability to strengthen by cold working as well as no
ability to remove possibly existing coarse-grained microstructure
by heat treatment. Unfortunately, the relative low hardness of this
material (about 200 HV) and its poor wear resistance causes its limited
applying, especially, under conditions of appreciable mechanical
wear (adhesive or abrasive) .
Many methods were developed in order to improve tribological
properties of austenitic steels. Some of them consisted in diffusion
treatment such as carburizing or nitriding. In paper , the process
of glow discharge-assisted low-temperature nitriding was reported.
It was carried out at 440°C (713 K) for 6 h resulting in the obtained
layer thickness of about 4 μm. Microstructure consisted of relatively
expanded nitrogen austenite and CrN nitrides. The increase in
the temperature up to 550°C (823 K) caused a significant increase
in the thickness of the layer to 30 μm and the appearance of iron nitrides
(Fe4N) in the microstructure [3, 4]. Cr2N was also often identified
in the nitrided layer . The process of low-temperature plasma
carburizing at the temperature below 520°C (793 K) resulted in
a microstructure consisting of expanded austenite [6÷9]. The low
temperature carburized layer was precipitation-free and consisted
of a single expanded austenite phase with an expanded fcc lattice
due to the supersaturation . At higher process temperature, i.e.
550÷600°C (823÷873 K), the thickne więcej »
Laser boronizing, which means alloying the substrate material with
boron by means of a laser beam, is a technology which is being
more and more commonly used in surface engineering thanks to
developments in laser technology and the availability of lasers of
newer and newer generation [1÷4]. Examples of research into the
processes of alloying with various chemical elements, including boron
with the use of laser beam can be found in Polish and foreign
publications as early as at the end of 20th century [1, 5÷7] as well
as in contemporary papers [8÷25]. Amorphous boron is used for
laser alloying most frequently [5, 7, 11, 12, 24], but there are also,
other compounds and phases, such as iron-boron, boron oxide, boron
nitride, boron carbide or mixtures of these phases [6, 8÷10].
The alloying element can be introduced by means of paste which
is applied beforehand or indirectly into material in the pool of the
remelted substrate material.
The equipment applied in the process is most commonly used
in the technology of cutting, boring, welding, thus CO2 molecular
lasers [6, 7, 11, 12, 19], but also diode ones  or YAG type .
Laser treatment is an effective method because in case of quick
heating and cooling there is an increase in properties of the treated
material thanks to fine-grained microstructure that is formed in the
surface layer, with newly produced metastable phases (after boronizing
it is phase Fe3B [16, 19]), their defects and large compressive
stresses that emerge in the process [1, 2].
The structure and properties of boronized layers obtained by laser
are comparable to those achieved after conventional diffusive
boronizing [3, 4, 14, 15] or after the laser remelting of diffusive
layers of iron borides [4, 25]. It is found that laser boronizing can
be an alternative to diffusive processes because it produces surface
layers with similar microhardness and frictional wear resistance
[14, 17, 20, 22], wi więcej »
Roller bearings are successfully used to change the sliding friction
to the rolling friction in combinations of machine elements mobile
nodes. The bearings are widely used in the various elements of machinery
and equipment from domestic appliances, through machine
industry and finally heavy industry. According to this statement
monitoring process of the state rotating bearing elements is a very
important matter. Negligence in diagnostics, maintenance and replacement
after a course or during work time can lead to extend
downtime of machinery and equipment.
2. DURABILITY, WEAR AND FATIGUE
OF ROLLING BEARING
Durability of rolling bearings is strongly dependent on the operating
conditions such as character of the load, rotation speed, temperature,
work conditions and environment (humidity, dustiness and the
corrosion aggressiveness of environment). Based on parameters
above, we might calculate the fatigue life of the bearing which forecasting
is quite necessary. Manufacturers of the bearings in their
catalogues publish approximate times of proper operation of bearings.
Technical condition of bearing monitored by service life used
vibroacoustic methods, depending on strategy users and services.
Replacement of the bearing occurs after finding its bad technical
condition. The second strategy used is responsible device nodes exchange
the bearing after the end of its service life provided by the
producer. This strategy is commonly used. To increase of reliability
and fatigue life of bearings developmental studies are realized by
the Authors. Noises generated during normal operation, vibration
and higher temperature of the outer bearing race it basic analysed
work parameters of bearings.
The main assessment of bearing fatigue is visual and vibroacoustic
assessment of the raceway and rolling elements. Based on
this, we can conclude what is the main effect of bearing damage.
This is conducive to prevent other bearings da więcej »
The life of many machine parts can be significantly extended by
enhancing the tribological properties of the surfaces. Better durability
of surfaces can be achieved by coatings of appropriate materials.
Coatings with various desired properties have been already developed
and are already widely used with great economical benefits.
The technologies, that have been developed for this purpose, are
referred to as Surface Engineering.
There is an ever increasing requirement for low cost coatings
with high quality tribological properties of its surfaces for wider
applications with combined requirements. Examples are machine
elements subjected to sever conditions, such as friction and wear,
corrosion, or exposure to high temperature. For example, coatings
of shafts of rotating machinery have combined requirements. There
is a need to increase the hardness of the surfaces rotating inside the
bearings to resist wear, and increase the load capacity of the surface,
while the core of the shaft must retain its original plasticity, in order
to prevent failure due to brittle cracking under the impact forces
in operating machinery. In addition, the coating must have good
bonding to the substrate material of the machine element in order to
avoid undesired peeling (delamination). It has been already realized
that heterogeneous surfaces, are advantageous for such combined
requirements. They are designed to have the desired distribution of
composition and gradients of various properties, such as microhardness,
along the thin width of the coating.
There are many methods for surface coatings such as electroplating
or plasma spraying [1÷6]. Very thin layers can be deposited by
vapour deposition. Various surface treatment techniques have been
developed to improve the desired properties of the deposited layers,
based on the substrate material. One important low cost method is
the electro-spark deposition (ESD), which has been recognized więcej »
Proper surface preparation for the hot-dip zinc-coating process is
the key issue of correctness and quality of the above process’ execution.
Apart from surface purity and the degree to which it is developed,
it is important to determine the degree of its wettability, which
affects the quality of the manufactured zinc coatings. The wetting
with a given liquid is represented by its tendency to spread over
a solid’s surface. The capacities of a given liquid to spread over the
surface can be determined by measuring the angle between the liquid
and the solid’s surface. It is determined by the direct measurement
of the angle between the tangent at the point of the two phases’
contact and the substrate. If liquid particles are more strongly attracted
by the solid ones, the liquid spreads more over the surface.
In the case of weaker attraction, there is a weaker wetting of the
surface. The greater tendency to wet the surface is, the smaller the
contact angle is, until a complete wetting at an angle equal to zero
. It is accepted that if, for water as a test liquid, θ < 90°, the surface
is hydrophilic, and if θ > 90° — it is hydrophobic. This is undoubtedly
important in the later behaviour of metal-coating systems
and their strength.
In this paper, we raised the question of the steel substrate’s wettability
for the zinc-coating process after various surface preparation
One of the most widely used in the industry is subcritical annealing
applied primarily in process systems of continuous zinc-coating .
The task of the subcritical annealing in atmospheres is mainly
cleansing the surface of products and residues after rolling and storage
(of lubricants and protections) but also, the reduction of surface
oxidation products, especially in the case of materials, on the surfaces
of which oxides more durable than iron oxides form [3÷6].
This is particularly importan więcej »
With the development of clinical methods and dental materials,
composites have become one of the most commonly used materials
for the reconstruction of hard tissues of the tooth, while meeting the
needs of physicians and patients . Since the introduction to the
market — that is over half a century ago, researchers have focused
on improving their properties, especially to increase the comfort
of their clinical use . Unfortunately, composite materials despite
continuous improvements have also some disadvantages. Curing
processes of dental composites is accompanied by the phenomenon
of polymerization shrinkage . It causes formation of shrinkage
stresses in the composite material and the tooth-restoration interface
. These stresses can lead to various complications such as
deformed tooth structure or even cracks in healthy tooth structure.
Other consequences of the contraction stress reported in the literature
are: post-operative sensitivity, damage of the adhesive bond
between restoration and tooth tissue, marginal discoloration and
secondary caries [5, 6]. Therefore, the elimination or reduction of
volumetric shrinkage during the polymerization processes is one of
the major problem in the development of dental composites. Dental
composite polymerization shrinkage ranges from 2% to 6% by
volume . Its volume depends on the type, quantity, degree of
conversion and molecular weight of the monomers. In addition, an
important factor is the type, geometry of the grains and the percentage
of filler concentration [3, 8]. Baroudi K. et al. concluded that
increasing amount of filler fraction in flowable composite decreases
the value of the volumetric polymerization shrinkage . It has also
been proven, that the modification of the polymerization process
of dental composites is one of the important factors affecting the
final properties and generated by the material shrinkage stresses
[10, 11]. It is p więcej »
Podstawę prawną odmowy wszczęcia postępowania administracyjnego
stanowi art. 61a § 1 k.p.a.1. Zgodnie z przywołaną normą, gdy żądanie,
o którym mowa w art. 61 k.p.a. (czyli żądanie strony, na podstawie którego
wszczyna się postępowanie administracyjne) zostało wniesione przez osobę
niebędącą stroną lub z innych uzasadnionych przyczyn postępowanie nie
może być wszczęte, organ administracji publicznej wydaje postanowienie
o odmowie wszczęcia postępowania. Analizowany przepis wskazuje dwie
samodzielne i niezależne przesłanki wydania postanowienia o odmowie
wszczęcia postępowania administracyjnego. Pierwszej z tych przesłanek
k.p.a. nadaje wymiar podmiotowy (wniesienie podania przez osobę niebędącą
stroną), a drugiej wymiar przedmiotowy (zaistnienie innych uzasadnionych
przyczyn uniemożliwiających wszczęcie postępowania).
Odnosząc się do przesłanek formalnych, o których mowa w art. 61a
§ 1 k.p.a., warunkujących możliwość wszczęcia postępowania administracyjnego,
należy na wstępie podkreślić, że stosownie do art. 61 § 1 k.p.a.
1 Ustawa z dnia 14 czerwca 1960 r. Kodeks postępowania administracyjnego
(t.j. Dz.U. z 2017 r. poz. 1257) [dalej: k.p.a.].
postępowanie administracyjne wszczyna się na żądanie strony lub z urzędu.
Pojęcie "strony postępowania administracyjnego" zdefiniowane zostało
w art. 28 k.p.a., w rozumieniu przywołanej normy prawa "stroną jest każdy,
czyjego interesu prawnego lub obowiązku dotyczy postępowanie albo kto
żąda czynności organu ze względu na swój interes prawny lub obowiązek".
W świetle art. 28 k.p.a. zasadnicze znaczenie dla ustalenia kręgu podmiotów,
mających przymiot strony postępowania administracyjnego, ma zatem
określenie "interesu prawnego lub obowiązku" wnioskodawcy.
W orzecznictwie Naczelnego Sądu Administracyjnego2 utrwalone jest
stanowisko, iż o istnieniu interesu prawnego decydują przepisy prawa materialnego,
przyznające stronie konkretne, indywidualne uprawnienia. Interes
taki powinien b więcej »