1. studied the effect of pre-hardening of steel


1.       (IGARTUA)  Firstly, Low temperature PVD process to
achieve the coatings at limited temp. of 160 C has been described by applying
the newly developed technique namely “Enhanced Sputter Ionic Plating” .
Secondly, the characterization of coatings in lubricated conditions was done by
analysing the tribological test results.
Titanium derivative coatings resulted an increase in hardness which in turn
improved tribological performance under high stress conditions.  CrN
coatings exhibited improvement under low load, high speed working conditions.

2.       (NAVINSEK)
The CrN and TiN hard coatings of thickness of 3µm at a temperature of 200
°C were applied on steel, sapphire and alumina substrates by plasma beam
sputtering process and the effect on various characteristics was studied. Their
oxidation behaviour was studied at temperatures up to 600 °C for TiN and up to
800 °C for CrN coatings and the results showed that a stoichiometric CrN coating
can remarkably be applied as a hard and oxidation-resistant
coating in real industrial environment, even if the working temperatures are
higher than 750 °C.

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)Effect on tribological properties of low alloy steel, under low load and low
speed, was studied by applying the duplex coating consisting of 500 ?m thick low pressure carburizing layer and 2 ?m thick layer of Cr–(WC–Co) coating deposited by dual RF
magnetron sputtering. Experimental results showed that sliding wear, of the
investigated duplex treated low alloy steels, is strongly dependent on the
counterface materials. While the wear performance of a Cr–WC coating (Cr/W ratio of 1.12:1) deposited onto the surface of
a carburized low alloy steel (0.61wt. % C; HV=654±5) was recommended the best,
the duplex-treated samples suffered severe, concentrated wear against alumina.
This wear is characterized by a combination of delamination, mild abrasion and
oxidative wear.


Baragetti(2007) Investigated the effect on fatigue
resistance of CrN-PVD coated spur
gears used in gearboxes for automotive applications by employing the numerical simulation of crack propagation to
determine the number of cycles necessary to reach specified crack depths in
coated and uncoated steel and titanium spur gears. Results showed the
improvement in the fatigue life of coated gears over the uncoated gears.


Komarovs et al. 2016 studied the  effect of pre-hardening of steel substrate on
mechanical and tribological properties of TiN and TiAlN coating–steel
substrate composites and found that prior nitrocarburization of the steel
substrate increased the microhardness by 7 times, the wear resistance of the
working surface of the composite upto 2.3 times &  the resilience 
by 4.5 times. A method was suggested to determine wear resistance of the
deposited coatings  &  the influence
of the hardness gradient and contribution of all layers to overall durability
of such layered systems.



Souza et al.2009 carried the plasma
carburizing of AISI 316L at 480 °C
and 400 °C, during 20 h, using CH4 as carbon carrier gas allowing  introduction of carbon at temperatures below
500 °C without carbide precipitation
causing the lattice distortion. This lattice distortion resulting from the
expansion and the associated compressive residual stresses increased the
surface hardness to 1040 HV0.025.



Saini & Gupta2012 investigated the fatigue crack
propagation behaviour of some commonly used low alloy steels in case carburised
condition through fractographic observations on the fractured surfaces of
standard fatigue test specimens failed under four-point rotating bending
fatigue tests. Most of the fatigue cracks initiated at the surface even after
the induction of residual compressive stresses during case carburisation and
further the crack propagated in a trangranular mode in all steels. But the
subsequent crack propagation was dependent on the contents of alloying elements
in particular steel. Higher content of chromium exhibited more inclination
towards intergranular decohesion cracking.


Feng et al. 1999 experimentally investigated the effect of surface coatings of TiN & TiCN on the high cycle fatigue
life of Austempered ductile iron (ADI) castings. The results concluded that the
TiCN coating caused higher increase in fatigue life of ADI as compared with TiN
coating because of higher hardness of TiCN coatings. Also the increase in
fatigue life was higher for the small size castings as compared with the large
size castings because of higher nodule count in small size castings.


Casadeiand and Tului
2013 developed an
innovative surface treatment, consisting of two consecutive phases:  deposition by reactive plasma spraying (RPS)
of a thick hundreds of micrometres) composite Ti/TiN coating on the titanium
based substrate and deposition by PVD of a thin &hard TiN coating, on the
already deposited thick coating. While the Ti/TiN interlayer limited the
deformation of the composite system by minimising the effects due to the
mechanical response, the uppermost layer of low friction TiN not only increased
the wear resistance but also reduced the probability of debonding caused by
interfacial shear stress.


Chen et
al.  2015 experimental studied the improvement
in fatigue wear resistance of grey cast iron through “laser carburizing”. Experimental
results demonstrated that laser carburizing is a more effective means of
improving fatigue wear resistance than laser remelting and that the improvement
is significantly
affected by increase in energy density during treatment. Also it was revealed
that the unit not only removes the source of crack initiation, but also
eliminates the bridging of cracks throughout the material.


Asi et al
2007 evaluated the fatigue performance of gas carburized SAE 8620 steel
grades of different case depths achieved at typical carburizing times of 45
min, 3 and 5 h at the temperature of 940 °C.  Fractured specimens were examined for crack
initiation and growth characteristics of the materials in the core and
carburized case by SEM equipped with EDX. The decrease in bending fatigue
strength with the increasing case depths could be attributed to increase in internal
oxidation and non-martensitic transformation present at the surface.


et al. 2016, carried nano indentation test in the composite of expanded
martensite and small quantities of hexagonal ?-Fe24N10 iron
nitrides to estimate the mechanical properties and to obtain an energy
dissipation coefficient
in accordance of ASTMC1624 standard. The scratch test results showed a
correlation between the friction coefficient
and the energy dissipation coefficient.
As compared to the non-nitrided martensitic stainless steel, the expanded
martensite resulted a significant decrease in friction coefficient. The critical
load was 14N and tensile cracking was the mechanical failure mode of the nitrided


Sliwa et al.2015, 
found the possibility
of employing the FEM in the evaluation of stress distribution in multilayer
Ti/Ti(C,N)/CrN, Ti/Ti(C,N)/(Ti, Al)N, Ti/(Ti, Si)N/(Ti, Si)N, and Ti/DLC/DLC
coatings. The difference between the mechanical and thermal properties &
the structural changes which occur during the fabrication process caused the difference
in internal stresses in the zone between the coating and the substrate. An FEM
model in ANSYS was established to simulate the internal stresses in the
coatings and the correctness of this model was to be validated with
experimental results.


Beake et al.
2015, showed that tool
life of the coated tools could be improved by around 100% by applying the
bilayer of AlCrN–TiAlN coating as compared to monolayer of
AlTiN PVD coating. SEM was used to
evaluate the Failure mechanisms. The micro scratch testing revealed the
superior coating integration in case of   bilayer AlCrN–TiAlN
coating resulting in a very higher critical load required for fatigue failure
under wet milling conditions.


et al. 2017,
experimentally investigated the low cycle fatigue behaviour of duplex (plasma
nitrided and hard PVD coating) coated Cr-Mo-V steel which is used for the
forging die inserts in hot forging operations. The experimental results showed
a positive effect of PVD coating in high cycle fatigue regime but the effect
was negligible in low cycle fatigue regime. The low cycle fatigue parameters were
experimentally derived for uncoated and duplex coated surface of treated
Cr-Mo-V steel for operating temperatures of 150 ‘C and 500 ‘C.


et al. 2011, studied the effect of a PVD  WC/C coating on the fatigue behaviour of as
produced and foreign object damaged (FOD) solution heat treated and aged 7075 aluminium
alloy. Testing results showed that the WC/C coating improved the fatigue behaviour
of both smooth and especially damaged 7075-T6 specimens but the damaged WC/C
coated samples showed the worst fatigue behaviour, probably due to multiple
severe micro notches caused by the fractured coating.


2011 studied the rolling contact fatigue (RCF) behaviour of case-hardened
transmission gears for racing motorcycles by analysing the as-produced and
PVD-WC/C coated specimens. The experimental tests highlighted that, under
lubricated conditions, the RCF resistance of the WC/C-coated steel gears was
higher than that of the case-hardened ones and, therefore, the PVD WC/C coating
could be taken into account to improve the RCF behaviour of these components. 


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