On Factors Influencing Macro Shrinkage Porosity Formation in Compacted Graphite Iron

2014 ◽  
Vol 790-791 ◽  
pp. 429-434 ◽  
Author(s):  
Sadaf Vazehrad ◽  
Jessica Elfsberg ◽  
Attila Diószegi
Keyword(s):  
Elevated Temperatures ◽  
Carbon Film ◽  
Shrinkage Porosity ◽  
Compacted Graphite Iron ◽  
Porosity Formation ◽  
Porosity Level ◽  
Compacted Graphite ◽  
Factors Influencing

The purpose of this work is to investigate the relation between macro shrinkage porosity level and the level of graphite nodularity, gaseous elements and the size of eutectic colonies in compacted graphite iron. Also, the internal shrinkage-pore surfaces were analyzed by SEM and EDS techniques. It was found that samples with higher shrinkage porosity level, contained higher level of graphite nodularity and number of eutectic colonies. Also, samples with higher level of gaseous elements (Hydrogen and Nitrogen) showed higher tendency to shrinkage porosity formation. Austenite dendrites with different morphologies were observed inside the pores, indicating that were formed at different times during solidification, and the surface of the pores were covered with a layer of carbon film indicating that the pores were internal, with no contact to the atmosphere at elevated temperatures.

Microstructural Evolution of Compacted Graphite Iron under Thermo-Mechanical Fatigue Conditions

2011 ◽  
Vol 409 ◽  
pp. 757-762 ◽  
Author(s):  
S. Ghodrat ◽  
M. Janssen ◽  
Roumen H. Petrov ◽  
Leo Kestens ◽  
Jilt Sietsma
Keyword(s):  
Mechanical Properties ◽  
Cast Iron ◽  
Elevated Temperatures ◽  
Easy Access ◽  
Compacted Graphite Iron ◽  
Microstructural Changes ◽  
Oxide Layers ◽  
Cooling Cycle ◽  
Compacted Graphite ◽  
Mechanical Fatigue

Cast iron components in combustion engines, such as cylinder blocks and heads, are exposed for long periods of time to elevated temperatures and subjected to large numbers of heating and cooling cycles. In complex components, these cycles can lead to localized cracking due to stresses that develop as a result of thermal gradients and thermal mismatch. This phenomenon is known as Thermo-Mechanical Fatigue (TMF). Compacted Graphite Iron (CGI) provides a suitable combination of thermal and mechanical properties to satisfy the performance of engine components. However, TMF conditions cause microstructural changes, accompanied by the formation of oxides at and close to the surface, which together lead to a growth in size of the cast iron. These microstructural changes affect the mechanical properties and accordingly the thermo-mechanical fatigue properties. The aim of this research is to provide insight into the microstructure evolution of CGI, with its complex morphology, under TMF conditions. For this, optical and scanning electron microscopy observations are made after cyclic exposure to air at high temperature, both without and with mechanical loading. It was found that the oxide layers, which develop at elevated temperatures, crack during the cooling cycle of TMF. The cracking results from tensile stresses developing during the cooling cycle. Therefore, paths for easy access of oxygen into the material are formed. Fatigue cracks that develop also show oxidation at their flanks. In order to quantify the oxide layers surrounding the graphite particles, Energy Dispersive X-Ray Analysis (SEM-EDX) and Electron Probe Micro Analysis (EPMA) are used.

Tensile properties and microstructure evolution of compacted graphite iron at elevated temperatures

2019 ◽  
Vol 33 (01n03) ◽  
pp. 1940007
Author(s):  
Hongyan Duan ◽  
Zhiming Wang ◽  
Ming Song
Keyword(s):  
Elevated Temperatures ◽  
Fatigue Loading ◽  
Dynamic Strain ◽  
Detonation Pressure ◽  
Compacted Graphite Iron ◽  
Damage Mechanisms ◽  
Compacted Graphite ◽  
Long Time ◽  
Dislocation Movement ◽  
Increasing Temperature

Attention has been focused on the fatigue problem for compacted graphite iron, when detonation pressure and temperature becomes higher and higher in combustion chamber for a long time. The compacted graphite iron plays an important role in the cylinder head of diesel industry for its good combination of thermal and mechanical properties. The damage mechanisms of compacted graphite iron under fatigue loading are observed in this study by scanning electron microscope (SEM) and in situ technique at elevated temperatures. The results show that tensile strength of compacted graphite iron decreases slightly at first, then decreases dramatically with the increasing temperature, which is a common phenomenon, even of various metallic materials. For the compacted graphite iron, these two stages are mainly controlled by different transformation mechanisms: the former mechanism, slip band stage, is affected by the inhibition of dislocation movement including strain strengthening, dynamic strain aging and precipitation hardening; and the latter, boundary sliding stage, is controlled by the vacancy diffusion. The newly proposed mechanisms can provide a new clue for the optimization of cast iron design. These damage mechanisms lay the foundation for the application of the crack technology.

scholarly journals Interfacial debonding in compacted graphite iron: effect of thermal loading

2020 ◽  
Vol 28 ◽  
pp. 1286-1294
Author(s):  
Evangelia Nektaria Palkanoglou ◽  
Konstantinos P. Baxevanakis ◽  
Vadim V. Silberschmidt
Keyword(s):  
Thermal Loading ◽  
Interfacial Debonding ◽  
Compacted Graphite Iron ◽  
Compacted Graphite

Effects of Mo and Ni on the thermal conductivity of compacted graphite iron at elevated temperature

2019 ◽  
Vol 32 (5-6) ◽  
pp. 243-251 ◽  
Author(s):  
Dongmei Xu ◽  
Guiquan Wang ◽  
Xiang Chen ◽  
Yanxiang Li ◽  
Yuan Liu ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Elevated Temperature ◽  
Compacted Graphite Iron ◽  
Compacted Graphite

Cutting Tool Wear and Mechanisms of Chip Formation During High-Speed Machining of Compacted Graphite Iron

2007 ◽  
Author(s):  
Niniza S. P. Dlamini ◽  
Iakovos Sigalas ◽  
Andreas Koursaris
Keyword(s):  
Tool Wear ◽  
Surface Finish ◽  
Failure Criterion ◽  
Cutting Tool ◽  
Flank Wear ◽  
Cutting Tools ◽  
Compacted Graphite Iron ◽  
Crater Wear ◽  
Compacted Graphite ◽  
Cutting Speeds

Cutting tool wear of polycrystalline cubic boron nitride (PcBN) tools was investigated in oblique turning experiments when machining compacted graphite iron at high cutting speeds, with the intention of elucidating the failure mechanisms of the cutting tools and presenting an analysis of the chip formation process. Dry finish turning experiments were conducted in a CNC lathe at cutting speeds in the range of 500–800m/min, at a feed rate of 0.05mm/rev and depth of cut of 0.2mm. Two different tool end-of-life criteria were used: a maximum flank wear scar size of 0.3mm (flank wear failure criterion) or loss of cutting edge due to rapid crater wear to a point where the cutting tool cannot machine with an acceptable surface finish (surface finish criterion). At high cutting speeds, the cutting tools failed prior to reaching the flank wear failure criterion due to rapid crater wear on the rake face of the cutting tools. Chip analysis, using SEM, revealed shear localized chips, with adiabatic shear bands produced in the primary and secondary shear zones.

scholarly journals Scratch Behaviour of Silicon Solid Solution Strengthened Ferritic Compacted Graphite Iron (CGI)

2018 ◽  
Vol 925 ◽  
pp. 318-325
Author(s):  
Rohollah Ghasemi ◽  
Anders E.W. Jarfors
Keyword(s):  
Solid Solution ◽  
Normal Load ◽  
Scratch Test ◽  
Scratch Resistance ◽  
Compacted Graphite Iron ◽  
Depth Of Penetration ◽  
Scratch Depth ◽  
Compacted Graphite ◽  
Diamond Indenter ◽  
Different Content

The present study focuses on scratch behaviour of a conventional pearlitic and a number of solid solution strengthened ferritic Compacted Graphite Iron (CGI) alloys. This was done by employing a single-pass microscratch test using a sphero-conical diamond indenter under different constant normal loads conditions. Matrix solution hardening was made by alloying with different content of Si alloy; (3.66, 4.09 and 4.59 wt%. Si) which are named as low-Si, medium-Si and high-Si ferritic CGI alloys, respectively. A good correlation between the tensile and scratch test results was observed explaining the influence of CGI’s matrix characteristics on scratch behaviour both for pearlitic and fully ferritic solution strengthened ones. Both the scratch depth and scratch width showed strong tendency to increase with increasing the normal load, however the pearlitic one showed more profound deformation compared to the solution strengthened CGI alloys. Among the investigated alloys, the maximum and minimum scratch resistance was observed for high-Si ferritic CGI and pearlitic alloys, respectively. It was confirmed by the scratched surfaces analysed using Scanning Electron Microscopy (SEM) as well. In addition, the indenter’s depth of penetration value (scratch depth) was found as a suitable measure to ascertain the scratch resistance of CGI alloys.Keywords: Silicon solution strengthening, CGI, Abrasion, Scratch testing, Scratch resistance

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