The goal of the presented investigation was to assess the impact of surface laser modification with the implementation of nickel and chromium on the microstructure and tribological behaviour of grey ...iron. Surface laser modification consisted of remelting the surface layer with simultaneous implementation of selected elements. In the first variant of treatment only nickel was implemented and in the second one, a combination of nickel with chromium together. This treatment was performed on an agriculture machine part made of grey iron and working in intensive friction conditions. The constituted surface layer was characterized by about 0.45 mm of depth and a 160 mm
area of the most exposed to wear of the treated part. In the case of both types of variants, the achieved surface layer microstructure was identified as homogenized with small grains. It involved nickel in the first variant of modification and nickel and chromium in the second one. The attained microstructure with nickel addition was characterized by nearly 800 HV0.1 of hardness (a 3.6-fold increase in comparison to its core material). The approximate hardness of 900 HV0.1 was achieved in the case of the microstructure enriched with nickel and chromium (over a 4-fold increase in comparison to the core material). The roughness of the surface after laser modification was reduced (nearly 3-fold) in comparison to the original surface of the part that was characterized by quite substantial coarseness. The wear test showed that Ni and Cr laser coatings increased resistance to abrasive wear resulting from the modification of the microstructure by the formation of martensite and grain fragmentation. Laser modified parts had a 2.5-fold smaller mass loss than untreated parts. Both types of performed variants: with the implementation of nickel and a combination of nickel and chromium gave comparable effects.
Machinability can sometimes be difficult to predict and be impacted by different characteristics of the castings. Inoculation, a key step in foundry process, is well-known to be a powerful tool to ...adjust the characteristics of castings in both grey and ductile irons. Some metallurgical cases were investigated to understand different machinability behaviors in correlation to their metallographic characteristics. Thus, two examples taken from grey iron processes are analyzed to illustrate how inoculation is required to adjust characteristics of iron castings, especially the modifcation of graphite characteristics and the prevention of micro-shrinkage, both parameters are well-known to have an impact on iron machinability. The study also illustrates the importance of the ratio Mn/S to guarantee the presence of manganese sulfdes in the matrix, benefcial for iron machinability.
The basic mechanisms of increasing the strength of alloys, including methods through the introduction of the melt coherent and incoherent crystallizing structural components of the alloy dispersed ...particles were considered. New data on the influence of ultrafine particles obtained from grinding wastes of tool steels (metal abrasive slime) and proposed as modifying additives on the structure and strength properties of gray cast iron are presented. The prevailing influence of metal component of metal-abrasive sludge on the properties of cast iron is revealed. The optimum amount of additives-modifiers were defined. The increase in the strength of cast iron mid 20 as a result of modification is equal up to 20%
In this paper, a grey iron was submitted to low temperature isothermal heat treatment, austempering, in order to obtain austempered grey iron (AGI). Tensile strength, Brinell hardness and ...tribological properties were determined for the as-cast condition and for two austempering conditions. The tribological properties were evaluated by pin-on-disk testing in dry and wet environments. The results show that AGI exhibit better mechanical properties than the as-cast grey iron. Also, the mechanical properties of AGI improve as the isothermal heat treatment temperature decreases. The wear resistance of AGI is better than the wear resistance of as-cast grey iron in both dry and wet conditions. In dry conditions the wear resistance of AGI increases as the isothermal heat treatment temperature decreases. On the other hand, the wear resistance of AGI in wet conditions increases as the isothermal heat treatment temperature increased. The results are explained in terms of the microstructural differences found between the materials under evaluation.
A three-stage model for the nucleation of graphite in grey irons has been proposed. Stage 1 involves formation of small oxide based sites (usually <2·0 μm) in the melt. Stage 2 involved precipitation ...of complex (Mn,X)S compounds (usually <5·0 μm) nucleated by stage 1 microinclusions. Finally, in stage 3, graphite nucleates on the sides of the (Mn,X)S compounds, which have low crystallographic misfit with graphite. Three groups of elements are important to sustain this sequence for effective graphite nucleation. These are strong deoxidising elements, such as Al and Zr, to form a high count of very small stage 1 microinclusions, Mn and S to sustain MnS type sulphide formation, and inoculating elements, which act in the first stage and/or in the second stage of the graphite nucleation sequence. Inoculating elements improve the capability of (Mn,X)S compounds to nucleate graphite. In inoculated irons, the (Mn,X)S compounds are more complex. They have a lower Mn/S ratio and higher capability to nucleate graphite, especially when preconditioning/inoculating elements contribute with a high count of effective stage 1 particles.
The results of studies on the effect of particles of metal-abrasive sludge used as a potential modifier of gray cast iron are presented in the article.
The influence of metal and non-metal components ...of the sludge is clarified and the prevailing influence of metal particles is established during the studies. The assumption is made about the mechanism of the effect of particulate additives from the viewpoint of self-organization phenomena in ultradispersed systems. The strength increase of cast iron CЧ
20 as a result of the introduction of slurries into the melt reaches up to 25%.
The paper presents the results of tests carried out on grey cast iron obtained in laboratory conditions. Cast iron EN-GJL-200 was enriched with REM at 0,3 % wt. in relation to the weight of the ...charge metal. The presence of REM was found only in some elements of the structure, i.e. in ferrite and in precipitations. An 18 % decrease in the coefficient of friction was observed for REM-modified cast iron as compared to the base cast iron.
In brickyard industry, smooth roll crusher is the most critical component in the brick production process. The main damage to the surface of the roll crusher comes from abrasion wear. Grey cast iron ...with a CE around 4.0 was chosen for the manufacture of these rolls crushers. Castings with various compositions in the basic Class 25 grey cast iron were cast with the combined effects of copper and chromium to study their effects on their castability, mechanical properties and wear. The casting parts were heated to 900 °C and quenched with forced air. Optical metallography, chemical analyses, Brinell hardness and Vickers microhardness, tensile tests and wear tests were used to characterize the ingots cast. All the cast irons made were hypoeutectoid with a microstructure consisting mainly of class A type graphite in a pearlitic matrix. The sensitivity of cast iron to the mass effect has been greatly reduced by appropriate and economical additions of copper and chromium. Normalization treatment, high cooling rate through the eutectoid transformation temperature interval and additions of Cu and Cr promote the formation of a finer and harder pearlite. All these factors contribute to increase the strength and hardness of alloyed hypoeutectic grey cast iron. The results showed that the quenched and tempered alloys had best wear resistance at 400 °C for alloyed grey cast iron (containing 0.62%Mn, 0.37%Cr, 1.21% Cu and 0.12%Mo).
본 연구에서는 주철-알루미늄 이종재료의 계면결합강도를 향상시키기 위하여 탈흑연 열처리를 통해 주철 표면에서 일정 깊이까지의 흑연을 제거하였다. 열처리 시간이 증가함에 따라 흑연이 제거되는 깊이는 증가하였으며, 열처리 시간과 깊이 사이에 선형 관계가 나타났다. 일정 깊이의 흑연이 제거된 주철에 알루미늄을 다이캐스팅 공법으로 주조접합하여 주철에서 흑연이 ...제거된 공간을 알루미늄으로 채운 후, 계면 반응 및 알루미늄 침투 깊이를 조사하고 계면접합강도를 평가하였다. 다이캐스팅 공법을 통한 알루미늄은 탈흑연 열처리된 주철 표면에서 일정한 깊이까지 채워지는 것으로 확인되었으며, 주철-알루미늄 계면에 금속간화합물이 생성되지는 않은 것으로 확인되었다. 계면접합강도는 열처리 시간과는 큰 관계없이 90MPa 수준의 접합강도를 나타내었으며 이는 탈흑연열처리를 하지 않은 소재의 접합강도 12MPa에 비해 매우 높은 강도이며, 주철의 탈흑연 영역에서 고압 다이캐스팅 공정에 의해 침투된 알루미늄 용탕이 응고되면서 언더컷 구조의 기계적 결합에 의한 것으로 생각된다.
In this study, to improve the interfacial bond strength of cast iron-aluminum dissimilar materials, graphite was removed to a certain depth from the cast iron surface through de-graphitization heat treatment. As the heat treatment time increased, the depth at which graphite was removed increased, showing a linear relationship between the heat treatment time and depth. Aluminum was filled to a certain depth on the de-graphitized cast iron surface through die-casting method, and no intermetallic compounds were formed on the cast iron-aluminum interface. The interfacial bonding strength showed a value of 90 MPa regardless of the heat treatment time, which is very high compared to the 12MPa bonding strength of the material without de-graphitization heat treatment. This result is thought to be due to the mechanical bonding of the undercut structure as the liquid aluminum, penetrated by the high pressure die-casting process, solidified in the de-graphitized region of the cast iron.
The mechanism of carbon diffusion in the as-cast and heat-treated grey iron and 304 stainless steel bimetallic composites was investigated in this study. A simplistic empirical model for the ...interface carbon diffusion was proposed and has been validated against the experimental data. A liquid-solid compound casting technique was used to fabricate the bimetallic composites. For the graphitizing annealing heat treatment, the bimetallic composite specimens were heated to 940 °C and held for 120 min and 240 min in an electric heating furnace. The proposed empirical model is based on the presence of eutectic carbides chill zone near the interface that formed during solidification of the liquid grey iron above the solid stainless steel substrate. It was found that the calculated carbon concentration profiles based on the proposed diffusion model were in good agreement with the experimental results.
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