TITLE:
A method of evaluating high temperature oxidation resistance in a base material
and weld materials.
FIELD OF THE INVENTION:
This invention relates to a method of evaluating high temperature oxidation
resistance in a base material and weld materials.
BACKGROUND OF THE INVENTION:
For many years the temperatures and pressures of steam boilers and turbines
were intentionally increased. These increases allowed for greater efficiencies in
steam and power production. Structural materials have to operate under extreme
condition of temperature, pressure and oxidising environment so materials
degradation due to oxidation at elevated temperature is a serious problem in
thermal power plant.
Such parts are generally fabricated by welding in large-scale. Welding produces
both metallurgical and mechanical discontinuities and performance of weld joints
is often the life limiting factor in applications where high temperature oxidation is
important. Weld joints consist of three interacting component parts as the
wrought base metal, the as-cast weld

metal and the micro structurally altered region of the base metal, i.e. the heat
affected zone (HAZ). The assessment of weld joint performance depends on how
the microstructural variation across it, in particular the extent, geometry,
distribution and property differences, affect the oxidation behavior of the weld
joint as a whole. On this basis, the analysis of weld performance in high-
temperature applications is considerably more complex than that of the base
metal.
The coal is mostly use fuel in thermal power plant. Coal is a complex and
relatively dirty fuel that contains impurity of sulfur, vanadium and sodium. During
combustion these impurity melts or vaporized and get deposited on metal in form
of solid deposits and get molten at their melting temperature. Hot oxidation is an
accelerated form of high temperature oxidation which occurs above 538°C
temperature. It occurs due to presence of salt contaminates such as Na2SO4,
NaCI, KCI and K2SO4 that combine to form molten deposits, which damage the
protective layer of oxides. At higher temperature deposits of these salts are
molten and can cause accelerated oxidation which is called "Hot oxidation".

The fossil fuel contains Sodium, Vanadium, Chlorine and Sulphur as impurities.
Sodium and Sulphur react to form Na2SO4 during combustion of fuel. Sodium
reacts with Chlorine form NaCI. These compounds known as ash, deposit on the
surface of materials and induce accelerated oxidation (hot oxidation) in energy
generation systems. Oxidation occurs when these molten compounds dissolve
the protective oxide layers, which naturally form on materials during gas
turbine/boiler operation. As soon as the metal is oxidized, the cycle starts over
again and high oxidation rates occur. Further, in coal-gasification processes, hot
oxidation is expected to be a problem because the gas environment generally
has large sulphur and low oxygen.
Patent number: 20120304480 teaches of an oxidation furnace for the oxidative
treatment of fibres, especially for producing carbon fibres, which, comprises a
process chamber arranged inside a housing, a blowing device for hot air, at least
one suction device arranged in an end region of the process chamber, at least
one ventilator that circulates the hot air through the blowing device, the process
chamber and the suction device, and at least one heating device arranged in the
flow path of the hot circulated air.

The suction device is formed from a plurality of vertically interspaced suction
boxes. Said boxes have at least one outlet for the hot air, and at least one inlet
for hot air, communicating with the process chamber and arranged in the
outward-facing side of the suction boxes, that is the side at a distance from the
centre of the process chamber.
Patent number: 20120094148 relates to Process for depositing a coating for
protection against oxidation and against hot corrosion on a superalloy substrate,
and coating obtained. The invention relates to a process for depositing a coating
for protection against oxidation and against hot corrosion on a metallic superalloy
substrate, characterized by the fact that it comprises the deposition of the
following successive layers on the substrate, a first layer of aluminium and of at
least one element capable of being alloyed with sulphur, a second layer of a
material that isolates said element capable of being alloyed with sulphur. The
element capable of being alloyed with sulphur is chosen from the reactive
elements: zirconium, hafnium, yttrium, silicon, and the rare earth elements:
cerium, lanthanum, gadolinium. The invention also relates to the coating thus
formed.

US Patent 4,616,574 also relates to a process for eliminating, reducing or
modifying slagging, convective tube fouling, corrosion, sulfur trioxide formation,
acid smut is described and also plume visibility by intermittently injecting
pressure-hydrated dolomitic lime consisting of porous, particles having a high
specific surface and a low settling rate in water into the interior of a combustion
system.
US Patent no.6117730 teaches about a Integrated method by using high
temperature oxide for top oxide and periphery gate oxide, a process for
fabricating an ONO structure for a MONOS type Flash cell having a core and a
periphery includes providing a semiconductor substrate. A first silicon oxide layer
is grown overlying the semiconductor substrate, and a silicon nitride layer is
deposited overlying the silicon oxide layer. Before depositing a second silicon
oxide layer of the ONO structure, a bit-line mask is performed for forming at least
one bit-line at the core. Thereafter, an ONO mask is formed to protect the ONO
structure during an etch of the periphery. After depositing and cleaning the
masks for the bit-line formation and the periphery etch, the second silicon oxide
layer is deposited to overlie the silicon nitride layer using an HTO deposition

process. By depositing the second silicon oxide layer after forming the ONO and
bit-line masks, degradation of the second silicon oxide layer is prevented, and
the top silicon oxide layer maintains a high quality.
United States Patent no is 3,539,467 Hot briquetting and oxidation of coal pitch
mixtures in preparing activated carbon, a process for the preparation of granular
activated carbon from coal which comprises hot briquetting of the coal together
with pitch, comminuting said briquettes, oxidation, carbonization and activation of
the granules to form granules of activated carbon having improved hardness to
better resist attrition and reduced pore volume in the greater than 10,000A range
as well as increased density.
US Patent No. 6218315 B1 HTO is directed to the (high temperature oxide)
deposition for capacitor dielectrics, Reliable HTO (High Temperature Oxide)
dielectrics are provided by a rapid thermal chemical vapor deposition (RTCVD)
process in which a low pressure and a high ratio of reactants, e.g., oxygen-
containing gas to silane-containing gas, is employed. Specifically, the reliable
HTO is formed by a rapid thermal chemical vapor deposition at temperatures of
from about 500° C. or above,

said rapid thermal chemical vapor deposition process being carried out at a
pressure of less than 80 Torr and in the presence of at least one oxygen-
containing reactant and at least one si lane-containing reactant, said reactants
having a ratio of oxygen-containing to silane-containing of about 25:1 or greater.
Semiconductor devices such as capacitors and transistors that include at least a
layer of the high temperature oxide of the present invention used as a dielectric
material are also provided.
US Patent 3,216,498 teaches about Effluent from partial oxidation of natural gas
injected in oil recovery process, Natural gas is subjected to partial oxidation with
the hot effluent from the oxidation injected into an underground formation to
provide hot Contact fluids Solvent liquids, and drive force for recovering oil from
the formation. In one embodiment liquid product, including methanol, is
recovered from the hot oxidation effluent before injection of the effluent into the
underground formation.
US Patent no. 3,152,893 relates to a Process for preventing oxidation of hot
worked parts This invention relates generally to the hot working of metals and
more particularly to an improved method for inhibiting the oxidation of metal parts
being hot worked. In hot working certain oxidation-

sensitive metals, it is conventional to use protective atmospheres when
preheating the metal part and also when hot working the part. This practice is
essential in order to preclude excessive scaling and to avoid contamination with
the nitrogen and oxygen in the air. Such contamination is ordinarily encountered
with cast-wrought materials, but it is particularly acute in the case of powder-
fabricated metal parts. In fabricating metal parts by powder metallurgy
techniques, the parts normally possess some degree of porosity during certain
phases of the operation, as for example, after cold compaction. Because the
pores may be partially interconnecting, even the innermost regions of the powder
fabricated part can be penetrated by contaminants such as oxygen and nitrogen.
By reason of this fact and because a porous metal compact presents a greater
amount of exposed surface area to the heating atmosphere, the extent of
contamination arising in porous metals may be severe as compared to that
occurring in cast wrought materials exposed to an oxidizing atmosphere.
CA 2124147 A1 relates to a partial oxidation process for the production of a
stream of hot clean gas substantially free from particulate matter, alkali metal
compounds, hydrogen halides, hydrogen cyanide, sulfur-containing gases, and
with or without ammonia for use as synthesis gas, reducing

gas, or fuel gas. A pumpable hydrocarbonaceous fuel selected from the group
consisting of liquid hydrocarbonaceous fuel or liquid emulsions thereof, an
aqueous slurry of petroleum coke, and mixtures thereof and wherein said
hydrocarbonaceous fuel contains halides, alkali metal compounds, sulfur,
nitrogen and inorganic ash containing components, is reacted in a gasifier by
partial oxidation to produce a hot raw gas stream comprising H2, CO, C02. H20,
CH4, NH3, HCN, HCI, HF, H2S, COS, N2, Ar, particulate matter, vapor phase
alkali metal compounds, and molten slag. The hot raw gas stream from the
gasifier is cooled in a radiant cooler and cleaned. Optionally, ammonia is
removed from the gas stream by being catalytically disproportioned into N2 and
H2. The process gas stream is cooled and halides and HCN in the gas stream
are reacted with a supplementary alkali metal compound to remove HCI, HF and
HCN. Alkali metal halides and alkali metal cyanide, vaporized alkali metal
compounds and residual fine particulate matter are removed from the gas stream
by further cooling and filtering. The sulfur-containing gases in the process gas
stream are then reacted at high temperature with a regenerable sulfur-reactive
mixed metal oxide sulfur sorbent material to produce a sulfided sorbent material
which is then separated from the hot clean purified gas stream having a
temperature of at least 1000.degree.F.

CN 103286145 mention about this invention discloses a method for representing
the pressing degree of a hot-rolled plate oxidized iron sheet. The method
comprises the following steps that a pressing degree index of the oxidized iron
sheet is used, the pressing degree index of the oxidized iron sheet is equal to the
quotient between the total depth of pockmarks formed in the surface of a hot-
rolled sample plate and the thickness of the hot-rolled sample plate, wherein the
total thickness of the pockmarks is the sum of the thicknesses of all pockmark
formed in the surface of the hot-rolled sample plate. The method for representing
the pressing degree of the hot-rolled plate oxidized iron sheet fills up the blank
that a method used for evaluating the pressing severity of the oxidized iron sheet
of the hot-rolled plate does not exist in the prior art.
CA 2727105 C is relating to a Improved low sulfur nickel-base single crystal
superalloy with ppm additions of lanthanum and yttrium A single crystal casting
having substantially improved high-temperature oxidation resistance, hot
corrosion (sulfidation) resistance, and resistance to creep under high
temperature and high stress is characterized by an as-cast composition
comprising a maximum sulfur content of 0.5 ppm by weight, a

maximum phosphorus content of 20 ppm by weight, a maximum nitrogen content
of 3 ppm by weight, a maximum oxygen content of 3 ppm by weight, and a
combined yttrium and lanthanum content of 5- 80 pm by weight. It has been
discovered that careful control of the deleterious impurities, particularly sulfur,
phosphorus, nitrogen and oxygen, in combination with a carefully controlled
addition of yttrium and/or lanthanum provides unexpected improvements in
corrosion and oxidation resistance, while also enhancing high-temperature, high-
stress resistance to creep, without any detrimental effects on other mechanical
properties, processing or productabiiity, particularly castability.
EP 0684321 B1 describes .a hot corrosion resistant nickel-based superalloy
comprising the following elements in percent by weight: Chromium 11.5-13.5
Cobalt 5.5-8.5 Molybdenum 0.40-0.55 Tungsten 4.5-5.5 Tantalum 4.5-5.8
Niobium 0.05-0.25 Aluminum 3.4-3.8 Titanium 4.0-4.4 Hafnium 0.01-0.06 further
optionally comprising: Carbon 0-0.05 Boron 0-0.03 Zirconium 0-0.03 Rhenium 0-
0.25 Silicon 00.10 Manganese 0-0.10 Nickel + Incidental Impurities balance
said superalloy having a phasial stability number NV3B less than 2.45.

U.S. Patent No. 4,677,035, which discloses a nickel-base single crystal alloy
composition consisting essentially of, in percent by weight, 8.0-14.0% chromium,
1.5-6.0% cobalt, 0.5-2.0% molybdenum, 3.0-10.0% tungsten, 2.5-7.0% titanium,
2.5-7.0% aluminum, 3.0-6.0% tantalum, and the balance nickel. However, the
alloy compositions possess relatively high strength at prolonged or repeated
exposure to high temperatures, are susceptible to the accelerated corrosive
effect of the hot gas environment in which components fabricated from the alloys
are exposed to when used in gas turbines.
U.K. Patent 2153848A discloses nickel-base alloys having a composition within
the range of 13-15.6% chromium, 5-15% cobalt, 2.5-5% molybdenum, 3-6%
tungsten, 4-6% titanium, 2-4% aluminum, and the balance essentially nickel
without intentional additions of carbon, boron or zirconium, which are fabricated
into single crystals. Although the alloys claim an improvement in hot corrosion
resistance accompanied by an increase in creep rupture properties, the need
remains in the art for single crystal superalloys for industrial gas turbine
applications having a superior combination of increased hot corrosion resistance,
oxidation resistance,

mechanical strength, large component castability and adequate heat treatment
response.
US patent no. 8354176 B2b also teaches about an Oxidation-corrosion resistant
coating, A metallic coating for protecting a substrate from high temperature
oxidation and hot corrosion environments comprising about 2.5 to about 13.5 wt.
% cobalt, about 12 to about 27 wt. % chromium, about 5 to about 7 wt. %
aluminum, about 0.0 to about 1.0 wt. % yttrium, about 0.0 to about 1.0 wt. %
hafnium, about 1.0 to about 3.0 wt. % silicon, about 0.0 to about 4.5 wt. %
tantalum, about 0.0 to about 6.5 wt. % tungsten, about 0.0 to about 2.0 wt. %
rhenium, about 0.0 to about 1.0 wt. % molybdenum and the balance nickel.
US 20130341197 A1 relates to Method for producing a high temperature
oxidation and hot corrosion resistant MCrAlX coating on a superalloy substrate
include applying an M-metal, chromium, and aluminum or an aluminum alloy
comprising a reactive element to at least one surface of the superalloy
component by electroplating at electroplating conditions below 100° C. in a
plating bath thereby forming a plated component and heat treating the plated
component.

EP 1404887 A4 is directed to a High temperature oxidation resistant ductile iron
A nodular or compacted graphite iron contains up to 6 % aluminum, with high
strength and good ductility over a wide temperature range, combined with
excellent hot oxidation resistance and improved thermal fatigue resistance
compared to ductile and SiMo ductile irons. The iron alloy of the invention
contains, in addition to iron, from about 1 to about 6 % aluminum, from about 2 to
about 4.5 % silicon, carbon in an amount where the weight percent carbon plus
1/3 the weight percent of silicon is up to about 5.2 %, greater than or equal to
about 0.02 % cerium and up to about 1.5 % molybdenum. All percentages are
based on the total weight of the composition. The compositions may further
contain up to about 7 % nickel by weight.
Stainless steels are widely employed in boiler components wherever high
temperature and oxidation are expected. Stainless steels play an important role
as corrosion resistant & oxidation resistant material. Austenitic stainless steels
have high ductility, low yield stress and relatively high ultimate tensile strength,
when compare to typical carbon steel. With austenitic stainless steel, the high
chromium and nickel content suppress the phase transformation from austenite
to a mixture of ferrite and

cementite, thus keeping the material fully austenite on cooling.
OBJECTS OF THE INVENTION:
An object of the present invention is to propose a method of evaluating high
temperature oxidation resistance in a base material and weld materials.
Another object of the present invention is to propose a method to find the high
temperature oxidation resistance with oxidizing environment.
BRIEF DESCRIPTION OF THE INVENTION:
According to this invention there is provided a method of evaluating high temperature
oxidation resistance in base and weld materials comprising: preparing a specimen
having base, weld and synthetic fly ash; subjecting the said specimen to the step of
gravimetric measure and dimensional measurement, measuring the temperature
exposed by the specimen and synthetic flyash in the furnace, removing the specimen
and taken for quantitative and dimensional measurement computing the gravimetric and
dimensional difference, evaluation of the high temperature.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
Figure 1 - Shows flow chart of the methodology for evaluation of high temperature
oxidation resistance
Figure 2 - Shows the methodology for evaluation of high temperature oxidation
resistance in the base metal specimen in simulated boiler condition with Indian coal ash/
fly ash
Figure 3 - Shows the methodology for evaluation of high temperature oxidation
resistance in the weld specimen in simulated boiler condition with Indian coat ash/ fly
ash
DETAILED DESCRIPTION OF THE INVENTION:
Coat-fired power plants, the high temperature side of the boiler contains ash,
alkali sulfates and NaCI, which at higher temperature of range 650*C-800°C
creates the oxidation environment. This mixture leads to oxidation of the base
metal as well as weld area. The oxidation rate depends on the temperature,
environment and time. Thus in present investigation, the specimen is heated in
the range of 600*C-800*C, to analyse the oxidation rate at higher temperature
range. Experiments are conducted to investigate the high temperature oxidation
resistance on super austenitic

stainless steel and its weld me nt. After several heating cycles the quantitative
evaluations are carried out A methodology for evaluating high temperature
oxidation resistance with different coal/fly ash and different high temperature
boiler materials and their weldments is invented. Initially the specimen was
weighed and its dimensions were measured. The specimen is loaded with
simulated boiler environment. Synthetic fly ash was prepared different
combinations of sulphate/ Chloride and actual coal ash/flyash. The temperature
experienced by the specimen is measured in the high temperature furnace with
thermo couple. The high temperature oxidation experienced by the specimen is
computed using quantitative measurements as well as dimensional
measurements. High temperature oxidation resistance was calculated for each
specimen with definite time duration. The following table is given to show typical
the high temperature oxidation rate measured at different temperature.



The methodology for evaluation of high temperature oxidation resistance in the
base/weld metat specimen in simulated boiler condition with Indian coal ash/ fly ash.is
given infigure-1.
The methodology has 7 parts for base material parts:
In figure a), in a tubular furnace (1) where a pre weighed test (base metal) (2) specimen
is taken in a boat(3) and exposed to synthetic flyash of different composition of Indian
fly ash/ coal ash (4). Thermocouple (5) is inbuilt with the furnace to record the
temperature. The pre weighed and known dimensions and known thickness, specimen
is kept in the furnace through the inlet with leak proof gasket(7). Now the specimen is
exposed to high temperature oxidation environment, so that specimen is under high
temperature and oxidation

environment. The specimen is kept for a specific duration depending on the material.
The specimen is removed through the outlet (6).
In figure (b) the same method as described in (a) is applicable for weld metal region, a
pre weighed all weld $pecimen(8) is exposed to high temperature oxidation
environment, so that specimen is under high temperature oxidation environment. The
specimen will be kept for a specific duration depending on the weld material. The
specimens prepared from base metal as well as welded specimens were taken for high
temperature oxidation resistance evaluation.

WE CLAIM:
1. A method of evaluating high temperature oxidation resistance in base and weld
materials comprising: preparing a specimen having base, weld and synthetic fly
ash;
subjecting the said specimen to the step of gravimetric measure and dimensional
measurement,
measuring the temperature exposed by the specimen and synthetic in the furnace,
removing the specimen and taken for quantitative and dimensional measurement
computing the gravimetric and dimensional difference,
evaluation of the high temperature.
2. The method as claimed in claim 1 wherein the said base is boiler material.
3. The method as claimed in claim 1 wherein the said weld is boiler material.
4. The method as claimed in claim 1 wherein the said synthetic fly ash is prepared with
combination of sulphate / chloride and actual coal or fly ash.
5. The method as claimed in claim 1 wherein the temperature of the furnace is in the
range of 600°C to 800°C.