Print ISSN: 1681-6900

Online ISSN: 2412-0758

Keywords : Pack cementation

Using of Pulsed Nd-Yag Laser in the Treatment of Thermal Spray by Aluminum and Diffusion Coating Phases of Low Alloy Steel

Abd Al- khalaq Fawzy Hamood

Engineering and Technology Journal, 2012, Volume 30, Issue 2, Pages 222-237

High power pulsed Neodymium doped Yttrium Aluminum Garnet-
(Nd– YAG)- laser with 1J power was used to fuse coatings containing a mixture of
FeAlO and Al. This mixture produced by aluminizing pack cementation treatment
and thermal spray of low alloy steel, That is for Studying the mechanical ,
surface and metallurgical properties for each coating system , and to make a
comparison before and after irradiation , and also the specified properties including
the coating thickness . Aluminum Coated samples were made by two advanced
techniques pack cementation and thermal spray methods in order to compare the
resulted coating layer properties before and after irradiation, and also to determine
the technique role from one hand ,also fusing effect and thermal residual stresses
role which resulted from irradiation in the variation of studied properties on the
other. Results showed that pack cementation coating layer has roughness, Micro
hardness and wear resistance higher than thermal spray coating layer. Irradiation
results was showed an improvement in studied properties, this was attributed to the
fusing, thermal residual stresses and laser rays role in refining the grains which are
in conjunction with finer microstructure . After irradiation a formation of a hard
phase (martensite) was recorded, this was attributed to the sufficient percentage of
carbon (0.4%) in the selected alloy, this was enshured by microstructure images
taken by optical microscopy. X-ray diffraction showed, for laser surface irradiated
coating layers, presence of the phase due to interaction between the base metal
constituents. A modification of coating phases composition could be concluded for
both coating techniques. Also the two techniques illustrate a formation of coating
layer with a different thickness.

Effect of Pack Cementation Coating on Hot Corrosion Resistance of Low Alloy Steel

Jawad Badr Gatea; Muna khedier Abbass

Engineering and Technology Journal, 2009, Volume 27, Issue 2, Pages 332-346

Two technique of coatings were performed by applying pack cementation
technology, the first one was aluminizing diffusion coated low alloy steel substrate
whereas the second one was single step simultaneous Co-deposition silicon- aluminum
diffusion coated low alloy steel substrate. The pack mixture used for producing both
coating systems in pack cementation process was composed of (30% Al, 2% NH4Cl and
the filler 68% Al2O3) , (30% Al , 5% Si , 2% NH4Cl and 63% Al2O3 ) respectively. The
pack temperature was 1000◦C and the diffusion time was 3 hr. XRD exhibits the phases
formed on both coated systems are Fe2Al5 , FeAl3 and FeSi . Uncoated low alloy steel
substrate and the both two coating systems were subjected to exposure environment
deposit salts mixture of (50%Na2SO4 and 50%NaCl) with weight (2mg /cm2), using
cyclic oxidation method in the experiments at temperature of 750◦C for 100hr each
cycle of 5hr. It was found that the oxidation kinetic for uncoated low alloy steel will give
evidence that the oxides formed on this alloy are non – protective. The XRD analysis
exhibited the phases are Fe2O3 , Fe3O4. It was found they followed linear rate law, and
spalling was observed. After these hot corrosion tests were undertaken, It was found that
the oxidation kinetics for both coated systems in environment consist of salt mixture
(50% NaCl +50% Na2SO4) followed parabolic law (protective oxidation behavior). XRD
exhibits the oxides formed on both coated systems are Al2O3, SiO2.

Isothermal Oxidation of Simple and Pt-Modified Diffusion Coating on Inconel Alloy 600 In Water Vapor

Khalil; Al- Hatab; Al- Alqawie; Hussein; Ahmed Ali; Moosa

Engineering and Technology Journal, 2009, Volume 27, Issue 2, Pages 288-299

In this work the oxidation behavior of both inconel alloy 600 and coated system
(Pt-modified aluminide coating) was investigated in pure water vapor H2O in the
temperature range 700 - 900 ºC. The platinum was deposited by electrochemical
method. Pt-modified aluminide coating was applied to inconel alloy 600 by using singlestep
high activity pack cementation method. The weight gain measurements indicate
that the oxidation kinetic is parabolic for uncoated and coated alloy. At temperatures
below 900 ºC the inconel alloy 600 is less aggravated in water vapor environments
because it is a chromia former alloy. At 700 ºC, water vapor does not have a significant
effect on the spalling of oxide scales. At 900 ºC, water vapor causes spalling of the
oxide scales during isothermal oxidation of inconel alloy 600. Therefore, it is concluded
that this alloy should not be used above 900 ºC in water vapor environments. Large
voids were found at the oxide scales-substrate interface and at grains or at grain
boundaries due to the chromium outward diffusion toward the oxide scales.
At 900 ºC, the parabolic rate constant (kp) of the coated system was one order of
magnitude lower than that for the uncoated alloy. It was concluded that, water vapor
exhibit little effect on the Pt-modified aluminide coating. Oxide phases that formed on
coated system are: Al2O3, NiAl2O4, Cr2O3, and NiFe2O4.