Effect of chill formation on the mechanical properties and microstructure of grey and nodular cast irons used in automotive industry

Two types of cast iron were employed in this work. Grey cast iron was the first type, and ductile was the second one. Two specimens of the grey cast iron sample were used; one was kept without heat treatment, and the second was completely heat-treated by ferritisation regime. The two specimens of ductile cast iron were used similarly; one was kept without heat treatment grey and the second was ferritised by heat treatment. Potentiodynamic technique was applied for collecting corrosion data of the above four metal specimens in HCl solutions in the absence and presence of thiourea as an inhibitor. The measurements were performed in different concentrations of HCl (0.05, 0.2, 0.5, and 1 M) at 20?C and in the absence of an inhibitor, on the other hand, corrosion parameters were collected in 0.2 M HCl at different temperature levels (20?C, 30?C, 40?C, and 50?C). Thiourea was added in different concentrations to 0.2 M HCl at 25?C, then corrosion data was deduced. An optical microscope was used to investigate the microstructure of grey and ductile cast iron before and after heat treatment. Corrosion resistance and corrosion rates were collected directly from potentiostat, where Tafel lines were applied to the software. The above raw data was used to deduce activation thermodynamic parameters (Ea*, &#916H?, and ΔS?) of dissolution processes in the absence of thiourea by applying Arhenius equation. Adsorption parameters, in the presence of thiourea, were deduced using the kinetic model and the Flory-Huggins isotherms were used as inhibition mechanisms for the investigation before and after treatment.

Erosion mechanisms of nodular and gray cast irons at different impact angles

The influence of nitriding on the fatigue resistance of grey and nodular (ductile) cast iron piston rings was studied for six chemical compositions. The selected materials include three grey cast irons: one with a mixed initial microstructure (martensite plus bainite), the second martensitic and another martensitic alloyed with niobium; and three nodular cast irons: one common nodular cast iron, the second alloyed with Nb and another alloyed with Al and V. These materials were gas nitrided for 3 and 6 h. The relationship between the mechanical behaviour and the treatment time (depth of nitrided layer) was established. Samples were tested under a cyclical bending load. The stresses were determined in the cross-section, where the biggest moment was experienced. Results were statistically treated by means of Weibull analysis. Nitriding showed that fatigue resistance of grey cast iron with a martensitic structure is higher than that of a mixed structure. Fatigue resistance of nodular cast irons is red...

This article describes the metallographic specimen preparation procedures for cast iron test samples, including mounting, grinding, polishing, and etching. It discusses the makeup and use of black-and-white and selective color etchants and where one might be preferred over the other. The article provides information on nearly 100 micrographs, discussing the microstructure of flake graphite in gray iron, nodular graphite in ductile iron, and temper graphite in malleable iron. It also examines the matrix microstructures of gray, ductile, compacted, and malleable cast iron samples.

The surface of gray cast iron has been modified by Tungsten Inert Gas (TIG) process. Welding current of magnitude 25, 35, and 45 amperes have been used to melt the surface of gray cast iron. Microstructural characterization, hardness measurement and dry sliding wear tests have been performed on these modified surfaces. It has been observed that increase in welding current caused the microstructure of grey cast iron to be gradually refined. Graphite flakes segregated between interdendritic regions in the as-received grey cast iron have been completely replaced by a uniform distribution of finer graphite flakes in the matrix. Hardness has been found to increase with increase in welding current. Wear resistance of the gray cast iron also increased with increase in the welding current reaching maximum value for 45 amperes. The increased hardness and wear resistance of these modified surfaces have been explained on the basis of microstructural changes occurring at the surfaces of gray cast iron. Keywords: Gray cast iron; Surface modification; TIG process; Dry sliding wear.© 2009 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved.DOI: 10.3329/jsr.vli3.2577 J. Sci. Res. 1 (3), 516-527 (2009)

Damping behaviour of micro alloyed ductile and gray cast irons were investigated in this study. This was aimed at establishing the effect of composition and microstructural parameters on the damping properties of the micro alloyed cast irons, which have shown promise for utilization in automobile and machine building where enhanced damping performance are vital. Gray cast iron containing manganese as base metal was micro alloyed randomly with molybdenum, nickel, chromium and copper at an amount not more than 0.2 % each; magnesium was added to the melt prior to casting. The microstructures show that both ductile and gray irons were developed, ductile irons consisted of pearlite and ferrite phases with their nodular graphite surrounded by the ferrite phase. The micro-alloyed ductile irons generally had higher storage (78906.39 – 120868.51 MPa) and loss modulus (78906.39 - 120868.51MPa) than the micro-alloyed gray cast irons and the ductile iron composition without alloying elements. Although the damping capacity of the composition without micro alloying elements was highest for all the cast irons (~ 0.085), but it failed at approximately 110 ᵒC, while most of the micro-alloyed ductile irons exhibited satisfactory capacity for vibration energy dissipation up to 190 ᵒC than the micro-alloyed gray irons.

In this work, the influence of heat treatment process and quenching in different quenchant media of medium carbon steel, gray and nodular cast iron with ferrite matrix on the hardness, ductility and corrosion rate of has been investigated. During this type of operations, the specimens were Austenizing at 900°C for one hour. Therefore, the specimens were quenched in different kind of oil as quenched medium (oil 20-50, oil 40, oil 90, and water as reference). The hardness , impact energy to measure the ductility, corrosion rate and microstructures were studied. From result of steel 0.47% carbon was clear increasing in hardness and decreasing in ductility with close varying values in oil quenchant kind comparing with as received specimen and water quenched one, corrosion rate decreased with heat treatment and quenching process due to formation of single face instead of double phase before heat treatment process which created galvanic cell. For gray and nodular cast iron it is noticeable that no changing in microstructure within heating for one hour at 900°C because the matrix in both cast iron types is ferrite, therefore no changing in mechanical properties under heat treatment process with time of one hour which is not sufficient to decomposition of graphite, but with comparison the hardness of gray cast iron is more than nodular one due to distribution of graphite flacks which increase the hardness and decrease the ductility as well as increasesing the corrosion rate compared with nodular cast iron. Microstructure of both types of cast iron have been studied after subjected the specimens to heat treatment at 1000°C and for 10 hours, the microstructures shown clear diffusion of some carbon in ferrite matrix around the graphite phase and under quenched some of martensite formed.

Multi-layer laser cladding analysis and high-temperature oxidative wear behavior of cast iron with a low expansion coefficient

The nitriding process can be effectively applied to steel with alloying elements. The higher the alloying element in the steel maximizes the mechanical properties, including hardness. However, the raw material can be costly, therefore using cheap materials (without alloys) is a challenge in increasing surface hardness through iron nitride formation. Furthermore Grey and nodular cast iron have different properties and characteristics in the structure. This research focuses on the ability of the cast-iron structure to affect the nitride layer formation. Gas nitriding was conducted in a fluidized bed reactor with a 550°C in 20 % N2 and 80 % NH3 atmosphere at a flow rate gasses of 0.7 m3/hr process temperature and holding for 2, 4, and 6 hours. Tests are conducted by observing the depth of hardening, SEM, and EDAX. According to the results, the nitriding process increases the surface hardness of cast iron. The highest hardness value is nodular cast iron with a holding time of 6 hours (345 HV) and a hardening depth of up to 20-micron meters. The compounds formed in the nitride layer include FeN, Fe2-3N, Fe4N, and Fe2N. The compound formed is strongly influenced by the treatment time. Furthermore, the comparison of nitriding treatment on gray and nodular cast iron was influenced by the flake and nodule structure. In general, the nodule structure is responsible for maximum hardness. The longer treatment time allows the nitrogen atoms to diffuse more to the surface, while the flake structure limits the absorption of nitrogen atoms into the surface of the cast iron. Characterization of Nodular Cast Iron shows that The hardening depth distribution trend due to the nitriding process in nodular cast iron was not much different from gray cast iron.

At this time the need for metals, especially iron and steel in the industrial world is increasing. One that is widely used is cast iron, there are several types of cast iron, namely gray cast iron, white cast iron, malleable cast iron, nodular cast iron. Nodular cast iron is included in the cast iron class, this type of cast iron is now widely used as a substitute for steel for machine components such as agricultural machinery, automotive, construction and others. For this reason, research was conducted to determine the level of hardness and impact of nodular cast iron (ductile cast iron) FCD-50. In this study, where the hardness test is used as the basis for research to determine the resistance of materials (tensile strength) and changes in the microstructure formed in nodular cast iron (ductile cast iron) FCD-50. This study uses the Heat Treatment method where the cooling process uses oil media. And after the process, a hardness test is carried out. The results of the study obtained were an increase in hardness value from 23.66 HRC to 56.07 HRC. The changes that occurred were greatly influenced by the oil cooling media and holding temperature (holding time) in the isothermal holding pattern.

Sarcosine was inserted between fatty chain and carboxylic group of lauric acid to obtain lauroyl sarcosine, and the corrosion inhibition of lauroyl sarcosine triethanolamine (LSTEA) was significantly improved. The synergistic mechanism of amide group and lauric acid was investigated by comparing the corrosion behavior on the surface of HT300 gray cast iron in 330 mg/L NaCl solution. The results showed that both lauryl triethanolamine (LATEA) and LSTEA could prevent corrosion. At 298 K, when 1000 mg/L inhibitor was added, the inhibition rates are 71.93% and 83.89%, respectively. The morphology analysis also verified that LSTEA had better inhibition properties than LATEA. Comparing the adsorption parameters and Density Functional Theory (DFT) calculation results, it was found that LATEA and LSTEA could spontaneously adsorb on the surface of gray cast iron as monolayer to form a stable protective layer. However, the chelation of amide group and the electron absorption effect could make the electron density distributed at the polar end of the whole molecule, covering the active sites at the interface to the maximum extent, so that LSTEA has more excellent corrosion inhibition for gray cast iron.

Effects of single-pass laser heat treatment on erosion behavior of cast irons

The shellfish in nature was taken as the biological model, and the coupling design was carried out on the surface of grey cast iron. With the help of advanced laser cladding technology, the unit body was prepared on the surface of grey cast iron, so as to obtain the bionic samples of grey cast iron with high wear resistance and fatigue resistance. The composition, hardness distribution, morphology and phase of the unit were analyzed by micro-hardness tester, scanning electron microscopy (SEM) and XRD. Thermal fatigue test and friction and wear test were carried out on bionic and untreated grey cast iron samples. The effects on fatigue resistance and wear resistance of bionic laser cladding and grey cast iron were studied by comparing the experimental results. It was found that the laser cladding has a compact structure and a metallurgical bond with the substrate. The hardness of the unit is 2 times of that of the grey cast iron substrate. The thermal fatigue resistance of the material is improved by bionic laser cladding. The bionic laser cladding preparation can greatly improve the wear resistance of materials.

Water main failures are very expensive for municipalities because they typically result in expenses associated with repair costs, flood damage, and loss of revenue to affected businesses. Water main failures also interrupt the operation of vital services, such as medical care and fire-fighting operations. Currently, millions of dollars are spent annually by the water utility industry and by municipalities on the repair of failed components of the water distribution infrastructure, such as components that are made from gray cast iron or "gray iron” pipe and ductile cast iron or "ductile iron” pipe. The rate of municipal water main failures is expected to increase as the existing cast iron infrastructure continues to age. The cost of repairing damages caused by broken water mains (and subsequent flooding damage) may become an important item in many municipal budgets. It is important to develop a corrosion program to prevent catastrophic failures of water mains. This paper presents a plan consisting of several phases including preassessment, indirect assessment, direct assessment, and integrity assessment of failed water mains. We will elaborate on the failure mechanisms, failure analysis protocols, and corrosion mitigation strategies for water mains that experience breaks. Water main breaks are mainly due to corrosive soil, pipe material, galvanic action, stray current corrosion, or microbiological induced corrosion (MIC). This paper provides an overview of corrosion issues commonly experienced by water main pipes, presents specific case histories involving graphitic corrosion, galvanic corrosion, stray current corrosion, and MIC. In this paper, we will introduce a graphitization sensor for condition assessment of water mains. This sensor can identify the location and extent of graphitization on water main.

초음파 속도를 이용하여 다양한 종류의 주철에 대해 미세구조와 품질 특성을 평가하였다. 상용으로 사용되는 3종의 회주철 및 3종의 구상흑연주철을 준비하였으며, 열처리 미세구조의 영향을 평가하기 위해 구상흑연주철을 어닐링 열처리를 다르게 하여 시편을 준비하였다. 초음파 전파 속도 측정, 미세구조(펄라이트 분율, 흑연의 길이 및 구상화율) 정량화, 경도 측정을 행하여 이들 파라미터 사이의 경험적 상관관계를 확인하였다. 구상흑연주철의 초음파 전파 속도가 회주철에서의 속도보다 크게 나타났다. 구상흑연주철에서 펄라이트 미세조직의 분율이 감소할수록 경도 및 초음파 속도는 감소하였다. 초음파 속도를 주철 소재의 품질관리를 위한 비파괴평가 파라미터로서 사용할 수 있는 가능성을 보여주었다. It was attempted to evaluate the microstructure and quality of various types of cast iron by ultrasonic velocity measurement. Three types of commercial gray cast iron and ductile cast iron were used for this investigation, respectively. One type of the ductile cast iron was heat-treated as a function of annealing time to produce different microstructure. Ultrasonic velocity measurement, microstructural analysis (pearlite area fraction, graphite length and nodularity), and hardness measurement were performed to find empirical correlations among these parameters. Ultrasonic velocity of ductile cast iron was markedly faster than that of gray cast iron. Ultrasonic velocity decreased with the decrease of fraction of pearlite structure. As a quality monitoring parameter of cast iron, potential of ultrasonic velocity was suggested.