Posted tagged ‘corrosion’

FAILURE ANALYSIS

August 23, 2011

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• Why ?

As the standards of our industry rise due to increasing globalization and competition, there is an ever growing need for consistency and reliability. Breakdown of any unit, system or equipment is an avoidable and costly occurrence and must be prevented or minimized. Analysis of such failures becomes a resourceful and affordable tool in addressing such unwanted occurrences.

To establish whether the cause of component failure lay on:

a) Service conditions
b) Design considerations
c) Material and its specification
d) Improper processing and assembly procedures or
e)  Combinations of these.

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Only the real “Root cause” can ensure the effectiveness of corrective and preventive actions and avoid recurrence of failure.

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• Stages Of Failure Analysis

1. Understanding and assimilation of background data and selection of samples.
2. Examination and documentation of the failed part by the following

1. Visual examination of parts, location (if necessary) and relevant photographs as well.

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2.  Non destructive testing by means of Radiography, Dye      penetrant, Magnetic particle testing etc.

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3. Mechanical Testing for various physical properties.

3. Vital specimens are selected, classified, and subjected to:

  1. Macroscopic examination and analysis. This involves examining the fracture surfaces, secondary cracks, deposits and other such elements
  2. Microscopic examination and analysis of fracture surface (by Scanning Electron Microscopy, if required).

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4. Chemical analysis of material for conformation to specifications.

5. Chemical analysis of corrosion products, deposits, contaminants etc.

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6. The actual state of the failed part and the failure mode are established.

7.  Fracture mechanics study if found necessary.

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8. A simulation of the identical working environment to determine if any external      factors have contributed to the failure

9. Conclusions are determined after compiling all evidences and analysis and       then the report is generated.
10. Follow-up recommendations are also provided.

METALLURGY INTERVIEW

August 22, 2011

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  • What is the composition of Grey cast iron Grade 20?

Carbon      : 3.10 – 3.25%         Silicon : 1.75-1.95%    Manganese : 0.50 – 0.7%Sulphur : 0.05 – 0.07%       Phosporous : 0.04 – 0.07%

  • What is the composition of Cast iron Grade 35?

Carbon=2.90-3.10%Manganese=0.60-1.00%Silicon=1.50-1.90%Sulphur=0.10%

Phosphorus=0.15%  Chromium=0.30%        Molybdenum=0.30%   Cupper=0.25%

  • What are the super alloys?

Super alloys is an alloy that exhibits excellent mechanical strength and creep resistance at high temperatures, having good surface finish.

  • Why the Super alloys used for land-based turbines?

Super alloys are the top most alloys used for their excellent strength and corrosion resistance as well as oxidation resistance. No other alloys can compete with these grade.

  • What kinds of NDT methods are available?

1.Visual Inspection

2.Microscopy inspection

3.Radiography Test

4.Dye Penetrate technique

5.Ultrasonic testing

6.Magnetic Particle inspection

7.Eddy Current technology

8.Acoustic Emission

9. Thermograph

10.Replica Metallographic

  • What is Stress Corrosion cracking?

Stress corrosion cracking (SCC) is a process involving the initiation of cracks and their propagation, possibly up to complete failure of a component, due to the combined action of tensile mechanical loading and a corrosive medium.

  • What is meant by D2 Material used for Die tooling?

 

D2 – High Carbon Cold Work Tool Steel

D2 is a high Carbon, high Chromium, Molybdenum, Vanadium, Air hardening alloy tool steel which offers good wear resistance, high surface hardness, through hardening properties, dimensional stability and high resistance to tempering effect. D2 tool steel is also suitable for vacuum hardening.

Typical Composition

C.-1.50%

Si.-0.30%

Cr. -12.00%

Mo. -0.80%

V. -0.90%

  • What is Vacuum Induction Melting?

As the name suggests, the process involves melting of a metal under vacuum conditions. Electromagnetic induction is used as the energy source for melting the metal.

Induction melting works by inducing electrical eddy currents in the metal. The source is the induction coil which carries an alternating current. The eddy currents heat and eventually melt the charge