On-Site Nondestructive Metallographic Examination of Materials

2019 ◽  
Keyword(s):  
Metallographic Examination

Microstructure of Electro-Eroded Cemented Carbide Surfaces

1968 ◽  
Vol 26 ◽  
pp. 284-285
Author(s):  
V. N. Filimonenko ◽  
M. H. Richman ◽  
J. Gurland
Keyword(s):  
Surface Layer ◽  
Cobalt Content ◽  
Cemented Carbides ◽  
Face Centered Cubic ◽  
X Ray Diffraction ◽  
Metallographic Examination ◽  
Standard Procedures ◽  
Face Centered ◽  
Diamond Paste ◽  
Plastic Carbon

The high temperatures and pressures that are found in a spark gap during electrical discharging lead to a sharp phase transition and structural transformation in the surface layer of cemented carbides containing WC and cobalt. By means of X-ray diffraction both W2C and a high-temperature monocarbide of tungsten (face-centered cubic) were detected after electro-erosion. The W2C forms as a result of the peritectic reaction, WC → W2C+C. The existence and amount of the phases depend on both the energy of the electro-spark discharge and the cobalt content. In the case of a low-energy discharge (i.e. C=0.01μF, V = 300v), WC(f.c.c.) is generally formed in the surface layer. However, at high energies, (e.g. C=30μF, V = 300v), W2C is formed at the surface in preference to the monocarbide. The phase transformations in the surface layer are retarded by the presence of larger percentages of cobalt.Metallographic examination of the electro-eroded surfaces of cemented carbides was carried out on samples with 5-30% cobalt content. The specimens were first metallographically polished using diamond paste and standard procedures and then subjected to various electrical discharges on a Servomet spark machining device. The samples were then repolished and etched in a 3% NH4OH electrolyte at -0.5 amp/cm2. Two stage plastic-carbon replicas were then made and shadowed with chromium at 27°.

scholarly journals Investigation of Failure in Gas Turbines: Part 2 — Engineering and Metallographic Aspects of Failure Investigation

1993 ◽  
Author(s):  
Robert E. Dundas
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Heavy Duty ◽  
Metallographic Examination ◽  
Fracture Surfaces ◽  
Failure Investigation ◽  
Materials Used ◽  
Component Failures

This paper opens with a discussion of the various mechanisms of cracking and fracture encountered in gas turbine failures, and discusses the use of metallographic examination of crack and fracture surfaces. The various types of materials used in the major components of heavy-duty industrial and aeroderivative gas turbines are tabulated. A collection of macroscopic and microscopic fractographs of the various mechanisms of failure in gas turbine components is then presented for reference in failure investigation. A discussion of compressor damage due to surge, as well as some overall observations on component failures, follows. Finally, a listing of the most likely types of failure of the various major components is given.

Thermodynamic Analysis and Observation of Inclusions in Ferritic Stainless Steel with Rare Earth

2013 ◽  
Vol 662 ◽  
pp. 441-444
Author(s):  
Xiao Liu ◽  
Jing Long Liang
Keyword(s):  
Stainless Steel ◽  
Rare Earth ◽  
Ferritic Stainless Steel ◽  
Thermodynamic Analysis ◽  
Electron Spectroscopy ◽  
Thermodynamic Calculation ◽  
Metallographic Examination

The effect of RE on modifying inclusions of 430 ferrite stainless steel was studied by metallographic examination, SEM and electron spectroscopy. Thermodynamic calculation was used to analyze the formation of RE inclusions in 430 ferrite stainless steel. The result shows that sulfide and other irregular inclusions are modified to round or oval-shaped RE2O2S and RES.

scholarly journals The influence of manual metal arc multiple repair welding of long operated waterwall on the structure and hardness of the heat affected zone of welded joints

2017 ◽  
Vol 62 (1) ◽  
pp. 327-333 ◽  
Author(s):  
J. Pikuła ◽  
M. Łomozik ◽  
T. Pfeifer
Keyword(s):  
Heat Affected Zone ◽  
Welded Joints ◽  
Arc Welding ◽  
Power Plants ◽  
Welded Joint ◽  
Weld Bead ◽  
Boiler Steel ◽  
Metallographic Examination ◽  
Metal Arc Welding ◽  
High Degree

Abstract Welded installations failures of power plants, which are often result from a high degree of wear, requires suitable repairs. In the case of cracks formed in the weld bead of waterwall, weld bead is removed and new welded joint is prepared. However, it is associated with consecutive thermal cycles, which affect properties of heat affected zone of welded joint. This study presents the influence of multiple manual metal arc welding associated with repair activities of long operated waterwall of boiler steel on properties of repair welded joints. The work contains the results of macro and microscopic metallographic examination as well as the results of hardness measurements.

Thermodynamic Analysis and Observation of Inclusions in H13 Die Steel with Rare Earth

2013 ◽  
Vol 690-693 ◽  
pp. 193-196
Author(s):  
Xiao Liu ◽  
Jing Long Liang
Keyword(s):  
Rare Earth ◽  
Thermodynamic Analysis ◽  
Electron Spectroscopy ◽  
Thermodynamic Calculation ◽  
Metallographic Examination ◽  
Die Steel ◽  
H13 Die Steel

The effect of RE on modifying inclusions of H13 die steel was studied by metallographic examination, SEM and electron spectroscopy. Thermodynamic calculation was used to analyze the formation of RE inclusions in H13 die steel. The result shows that sulfide inclusions are modified to round RE complex inclusions after adding RE to H13 die steel.

Investigation of wear on the upper edges of webs of thin-film coated single-screw extruders processing pure polymers

2021 ◽  
Vol 63 (2) ◽  
pp. 143-150
Author(s):  
Torben Buttler ◽  
Jens Hamje ◽  
Rolf Reiter ◽  
Volker Wesling
Keyword(s):  
Wear Behavior ◽  
Cold Work ◽  
Polymer Processing ◽  
Chromium Nitride ◽  
Metallographic Examination ◽  
Test Speed ◽  
Single Screw Extruders ◽  
Pin On Disk ◽  
Screw Extruders ◽  
Disk Test

Abstract During polymer extrusion there are a variety of situations in which the screwthread of the extrusion screw has an unlubricated metal-to-metal contact with the barrel wall. At the same time the screw coating is subjected to the highest loads. The combination of a secondary hardening cold work steel 1.2379 and a chromium nitride coating deposited by ARC-PVD, which is frequently used in polymer processing, is characterized and investigated. The characterization is done by metallographic examination, SEM and CLSM. The tests were performed on a pin-on-disk and a pin-roll test rig. Different roughness levels were tested on the pin-on-disk test, where massive differences in wear behavior were found. A hybrid surface structure is proposed to optimize the tribosystem. On the pin-on-disk test stand, rollers made of the same material pairing were tested. The test speed was varied to highlight differences and similarities between the tribological systems. A wear minimization of 50 % was achieved and the similarities between the tribological systems were highlighted. In addition, the investigations led to the development of a new model thesis which provides a reason for the development of stippling on the screw when processing polycarbonate.

Stainless Steel Coatings for Corrosion Protection of Steel Rebars

1996 ◽  
Author(s):  
B. Arsenault ◽  
P. Gu ◽  
J.G. Legoux ◽  
B. Harvey ◽  
J. Fournier
Keyword(s):  
Stainless Steel ◽  
Carbon Steel ◽  
Salt Spray ◽  
Chloride Ions ◽  
Metallographic Examination ◽  
316 L Stainless Steel ◽  
Parking Garages ◽  
Coating Microstructure ◽  
Stainless Steel Coatings ◽  
Steel Rebars

Abstract Steel reinforcement corrosion is one of the most serious causes of the premature deterioration of North American bridges and parking garages. Carbon steel rebars are very vulnerable to corrosion in salt contaminated concrete from deicing or coastal environment since the chloride ions induce severe corrosion as they reach the reinforcing steel rebars and depassivate the carbon steel. This paper evaluates the potential of using stainless steel coatings as a means to protect steel rebars from corrosion, especially in a salt contaminated concrete environment. The 316 L stainless steel coated coupons and rebars were prepared using Arc-sprayed and HP/HVOF processes. The corrosion performance of coatings were evaluated using linear polarization, a.c. impedance and salt spray techniques. Metallographic examination was also performed to characterize the coating microstructure.

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