On-Site Metallurgical Analysis

On-site Metallurgy

As one of many services, FORCE Technology offers
metallurgical analysis of fully operational components
or of stationary or non-removable machine
parts, which we can analyse on-site, even without
having to cut samples.
On-site analysis of a material’s properties makes it
possible to target further analyses, repairs and countermeasures
in order to get the system back into
operation again faster and at lower costs.

Materials Properties
We look at properties such as:
• Microstructure
• Crack type
• Defect types in the material
• Hardness (for tensile strength estimation)
• Type of alloy (possibly using PMI techniques).

Metallurgical Testing
Using a relatively small number of tests, we can
check components on receipt to determine, whether
they meet the requirements and provide you with a
detailed description of the metal’s quality, its heat
treatment, actual final structure and strength level.
Materials defects that can be typed and classified
on-site as insignificant are often accepted, thus
avoiding expensive repairs and delays. On the other
hand, materials defects or structural changes that
are erroneously classified as harmless, but which are
actually critical, may have wide-ranging consequences
such as shorter component lifetime or system
failure.

In our experience, on-site metallurgical methods -
unlike traditional NDT methods - can predict many
structural failures long before they happen, failures
that can be avoided by making limited repairs or
changing operational procedures.

Inspection
Too little or no inspection of metal components is
often the cause for systems failing or extremely inconvenient
repairs having to be made. Any metallurgical
inspection has to be based on fundamental
knowledge of relevant failure mechanisms and correction
of conditions for failure if unforeseen damage
should occur. This involves identification of the defect
causing the damage — identification based either
on experience with the system or on detailed
examination of the damage.
The cause of damage can be determined by on-site
non-destructive test methods. Cracks, for example,
can be identified as fatigue cracking, creep, stress
corrosion cracking or hydrogen embrittlement, or as
pre-existing defects in the material. Information on
the type of damage will then be used to determine
changes to be made in operating conditions or materials
selection so that recurrence of such damage is
avoided.

High temperature operation or unintended exposure
to heat can result in gradual weakening in the metal
strength due to structural changes that can be revealed
and monitored by on-site microstructural
analysis and hardness testing. Data from these test
methods and from service logging can then be used
to determine remaining lifetime of the material. The
advantage is savings from planned repairs and replacement
rather than waiting for failure to occur.
This kind of testing is routine at many power and
chemical plants.
After a fire structural integrity is a key issue. On-site
metallurgical testing can reveal which components
are actually damaged and must be replaced, and
which components can be put back into operation
again without risk.

Replica Techniques
At FORCE Technology we have worked with replica
over the last 25 years. In our work we apply both
the replica technique using thin acetate foils as well
as the replica technique using a two-component
polymer silicone rubber.

- On smooth and prepared surfaces:
A material’s microstructure can be determined by
directly examining a polished and etched surface
using portable microscopes. In most cases, however,
even better results can be had by making a copy or
replication of a prepared surface for subsequent
laboratory analysis.
A replica of the surface is made by applying a softened
plastic foil to the surface. This foil moulds
itself to the metal surface when pressed. After its
removal from the metal, the plastic replica provides
an exact copy of the etched surface microstructure,
which can then be examined under our laboratory’s
high-quality and very high-resolution microscopes.

Such replicas can be stored for decades and subsequently
used in comparative analyses. The replica
technique can also be employed to determine types
and causes of cracking, or to reveal whether cracks
are propagating. An expensive repair of an insignificant
defect will often be avoided this way.
The replica technique is widely used on hightemperature
components in power stations and
chemical plants; it enables inspection of the most
critical parts of a plant during short shutdowns. The
technique can also reveal whether an austenitic
stainless steel has microstructural changes that
could induce lower corrosion resistance than required.

- On complex and rough surfaces:
FORCE Technology also offers replica inspection
using high-resolution silicone rubbers. This method
allows the replication of rough, uneven surfaces
even at elevated temperatures whether it be for
metallurgical examination or documenting surface
appearances. It opens the possibility of accessing
remote and difficult-to-access-locations in applications
such as boilers, engines, gearboxes, reaction
vessels, pipes, tubes, dies, internal cavities, boltholes
and a multitude of similar situations. Moreover,
silicone rubber replicas are also applicable in sub-sea
environments and in nuclear reactor installations.
After removal from test site the silicon rubber replicas
are used for metallographic microstructure assessment,
crack characterisation and for surface
finish and profile measurements of for instance machine
components.

Hardness Testing
Hardness testing provides indirect but vital information
as to the tensile strength or wear-resisting properties
of a material, information that would otherwise
have to be gained from testing large specimens,
cut out of the metal to be tested.
We have portable equipment for standardised tests
such as Vickers, Brinell and Rockwell C, as well as
more flexible equipment for Equotip and UCI testing.
Hardness measurements used to test high-strength
construction steel ensure optimum properties. If the
steel hardness in the heat affected zone is too high,
the steel may be vulnerable to hydrogen embrittlement,
which can lead to serious failures. Hardness
testing can also reveal insufficient heat treatment or
changes in strength properties, e.g. after a fire or
equipment overheating.
If the metals used in a structure or machine have
characteristics different than what is required, the
consequences are often shorter lifetimes, expensive
unscheduled shutdowns, or serious system failures.
On-site testing of these materials can reveal any
changes in properties or non-compliance with specifications
and thus help keep repair an maintenance
costs down.


Other services
Among other related testing services performed by
FORCE Technology are:
• Roughness measurements
• Stress measurements
• Coating thickness measurements
• Measurement of stainless steels’ ferrite content
• Chemical composition analysis.