In this issue, the effect of gas heat treatment ambient at the temperature of 950C
for 8hours using the gases NH3 or CH4 and using the gases NH3 and CH4 for
(4+4)hours of the distribution of the doping elements on Titanium alloys BT9 was
studied.
Oxide formation at the different treatment ambient as a reason of gas-phase
oxygen distribution to high depths in the samples was discovered.
We have studied in this paper the effect of thermal gaseous using NH3 – gas at some
diffusion layers properties of tool steel 20 in temperature range (550 ,650 ,750, 850) 0C ,
4h at each one . The purpose of this heat treatment is to get and determ
ine the microhardness,
fatigue and corrosion resistance.
The micro-hardness was determined using Vickers's tester with values ranged
between ( 130-435 ) HV.
In order to verify these results, we studied the microstructure if the surface layers
using metallurgical microscope and SEM (Scanning Electron Microscope). Furthermore
the corrosion resistance was studied after immersing it in sea water for two year.
Our results assured the presence of functional association between the
pigment epithelium (P.E) and photoreceptors of eye retina of lacerta laevis. The
continuous effect of He-Ne laser on eye produce dangerous structure changes
(according to studi
es by transmission electron microscope) led to damage of
parts and organelles of pigment epithelium and photoreceptors of eye retina.
The displacement of the epithelium from the photoreceptors layer was the first
dangerous results on vision (Retinal detachment). This detachment conduced to
no protection of photoreceptors from high intense light (which usually
maintained by melanin pigments spread in epithelium cells surrounding the
outer segments [O.S] of photoreceptors) so that the outer segments of
photoreceptor became under the influence of intense light of He-Ne laser which
conduced to damage of cytoplasmic membrane of outer segment disks and
damage of chemical structure of visual pigments (pigment necessary for
discrimination of color in cones) so the photo sensible pole lost its function in
transferring the sign of light necessary for vision. The lesion happened by the
influence of He-Ne laser in the cones, associated by dangerous changes in the
retardation of nucleus size and damage of chromatin material and the absence
of organelles responsible for biological synthesis of cellular protein, and
deconstruction of glycogen molecules (energy mols.). The most dangerous thing
is the resulted damage of synaptic pedicle of cones (lost of connection between
bipolar nerve cells and synaptic ribbons) so the neurotransmission pole lost its
function in neurotransmission across the layer of neurosynapsis of retina. The
damaged photoreceptor cells (cones) (which were almost dead) became disables
to do their function in vision.
