Effect of TiB2 Content on Properties of Nickel-Coated Graphite Self-Lubricating Coating Prepared by Laser Cladding

To improve the anti-wear and friction-reducing properties of self-lubricating coatings, Ni60/Nickel-coated graphite/TiB2 composite coatings with different contents were prepared by laser cladding. The coating properties were characterized by X-ray diffractometer (XRD), scanning electron microscope (SEM), energy spectrometer (EDS), electrochemical workstation, micro-Vickers hardness tester, and friction and wear tester. The results showed that with the increase in TiB2 content, the graphite morphology changed from spherical at 0 wt.% TiB2 content to a little black graphite alone at 14 wt.% TiB2 to irregular agglomerates at 22 wt.% TiB2. Furthermore, the hardness of the coatings increased with increasing TiB2 content, and the 63% Ni60 + 15% nickel-coated graphite + 22% TiB2 coating had the highest hardness. TiC and Cr7C3 were generated in the coatings with the addition of nickel-coated graphite, creating a dispersion reinforcement effect, so that the hardness of these coatings was higher than that of the 86% Ni60 + 0% nickel-coated graphite + 14% TiB2 coating without the addition of nickel-coated graphite. In addition, the 71% Ni60 + 15% Ni-coated graphite + 14% TiB2 coating had the lowest friction coefficient, wear loss, and wear volume, thus exhibiting excellent friction reduction and anti-wear properties. The 71% Ni60 + 15% nickel-coated graphite + 14% TiB2 coating had excellent corrosion resistance.

Study of Factors Affecting Tensile Strength of Grey Cast Iron

Tensile strength of a material is the capacity of material to withstand tensile force without failure. Tensile strength is important mechanical property of material which gives direction to use it for proposed application safely. It is very important parameter considered in designing sound product. Grey cast iron carries properties like high compressive strength, castable, good machinability, good abrasion resistance, high thermal conductivity, resist to expand under high temperature. Tensile strength of grey cast depends mainly on carbon content, steel scrap % used, inoculation, graphite morphology, cooling time. Present paper summarizes study of factors affecting tensile strength of grey cast iron. With the study of factors affecting the tensile strength of cast iron it is very helpful to achieve required tensile strength by controlling the factors affecting strength of the material. While studying and experimenting on the behavior of tensile strength, clear idea comes into the picture how the strength is affected.

Computational Determination of Macroscopic Mechanical and Thermal Material Properties for Different Morphological Variants of Cast Iron

The sensitivity of macroscopic mechanical and thermal properties of grey cast iron is computationally investigated for a variety of graphite morphologies over a wide temperature range. In order to represent common graphite morphologies according to EN ISO 945-1, a synthetic approach is used to algorithmically generate simulation domains. The developed mechanical and thermal model is applied in a large simulation study. The study includes statistical volume elements of the graphite morphology classes GJL-150 and IA2 to IA5, with 10, 11 and 12 v.−% of graphite precipitations, respectively, for a temperature range from 20 to 750 °C. Homogenised macroscopic quantities, such as the Young’s moduli, Poisson’s ratios, yield strengths and thermal conductivities, are predicted for different morphology classes by applying simulation and data analysis tools of the research data infrastructure Kadi4Mat. This is the first work to determine the mechanical and thermal properties of the morphology classes defined in EN ISO 945-1.

Development of Ductile Irons for High-Temperature Applications: Characterization in the As-Cast and Oxidized States

Ductile iron alloyed with molybdenum and different levels of aluminium and silicon was cast to determine the proper combination of elements to increase the temperature range of operation. Four alloys containing 1.5wt.% molybdenum and different combinations of aluminium and silicon (i.e. 3.5Si-3.0A1, 4.5Si-2.0Al and 4.5Si-3.0Al) were cast at 1350, 1400 and 1450⁰C into step blocks. The effects of alloy chemistry, pouring temperature and casting thickness in the as-cast and oxidized conditions were studied. Results from the as-cast condition show that graphite morphology (i.e., size, count and sphericity) improved with lower Si/Al ratios and intermediate pouring temperatures. Higher silicon and lower aluminium contents accompanied by intermediate pouring temperatures reduced the onset of surface and sub-surface defects. Results from the oxidized condition show that maximum oxidation resistance was achieved in alloys containing higher aluminium and silicon contents. This also increased the critical α-ferrite to γ-austenite phase transformation temperature range.

Development of Ductile Irons for High-Temperature Applications: Characterization in the As-Cast and Oxidized States

Ductile iron alloyed with molybdenum and different levels of aluminium and silicon was cast to determine the proper combination of elements to increase the temperature range of operation. Four alloys containing 1.5wt.% molybdenum and different combinations of aluminium and silicon (i.e. 3.5Si-3.0A1, 4.5Si-2.0Al and 4.5Si-3.0Al) were cast at 1350, 1400 and 1450⁰C into step blocks. The effects of alloy chemistry, pouring temperature and casting thickness in the as-cast and oxidized conditions were studied. Results from the as-cast condition show that graphite morphology (i.e., size, count and sphericity) improved with lower Si/Al ratios and intermediate pouring temperatures. Higher silicon and lower aluminium contents accompanied by intermediate pouring temperatures reduced the onset of surface and sub-surface defects. Results from the oxidized condition show that maximum oxidation resistance was achieved in alloys containing higher aluminium and silicon contents. This also increased the critical α-ferrite to γ-austenite phase transformation temperature range.

Influence of Aluminum on Fatigue Strength of Solution-Strengthened Nodular Cast Iron

The fatigue strength of high silicon-alloyed nodular cast iron is influenced by casting defects and graphite precipitates. The literature as well as the findings of this work show that these microstructural constituents can be tailored by controlling silicon microsegregation. In addition, segregations also affect the ferritic matrix microstructure locally. In the present work, silicon segregations in high silicon-alloyed ductile iron are specifically manipulated by small additions of aluminum. It was demonstrated how the aluminum content affects a wide range of microstructural constituents across a variety of length scales. Specimens from alloys with small additions of aluminum were fabricated and tested by rotating bending. Results show that the fatigue strength can be increased compared to a reference alloy with no aluminum. Microstructure analysis as well as fractography were performed concluding that microstructural changes could be attributed to the increased aluminum content, which allows the fatigue properties to be tailored deliberately. However, according to the results of this study, the negative effect of aluminum on castability and graphite morphology limits the maximum content to approximately 0.2 wt.%.

Ultrasonic Inspection for Microstructural and Mechanical Properties of Ductile Cast Iron

Ultrasonic inspection is a well-known method in non-destructive testing. Based on the changes in the ultrasonic sound speed, tested materials are evaluated in terms of internal defects. In addition to flaw detection, ultrasonic testing is used in the material characterization of ductile cast iron. Graphite shape detection has been widely investigated by ultrasonic inspection in literature. However, most of the measurements has been conducted at single frequencies. In this work, three different nodulizer included casting operations were carried out to produce ductile cast irons having various graphite morphologies. A wide frequency range of 1.25-10 MHz was selected in the ultrasonic inspection. In addition to graphite morphology analyses, the relationship between ultrasonic sound speed and mechanical properties was studied. In the mechanical analyses, hardness and tensile testing properties were investigated for the specimens. From the results, ultrasonic sound speed exhibits a considerable dependency to the graphite morphology. In addition to a good graphite detection capability, ultrasonic inspection exhibits promising results for predicting the mechanical properties such as hardness, elastic modulus, yield strength and tensile strength. It is also found that there is a slight increase in the ultrasonic sound speed by increasing the frequency, although sound speed is independent from this parameter.

Effects of aluminum and copper on the graphite morphology, microstructure, and compressive properties of ductile iron

The effect of aluminum (0, 2, 4, and 6 wt. %) and copper (0, 2, 4, and 6 wt. %) on graphite morphology, microstructure and compressive behavior of ductile iron specimens manufactured by sand casting technique were investigated. The graphite morphology and microstructure were evaluated using optical microscopy (OM) and scanning electron microscopy (SEM) equipped image processing software. To study the mechanical properties, the compression test was conducted on the ductile iron specimens. The results indicated that the surface fraction and nodule count of graphite decreased when the amount of aluminum increased from 0 to 2 wt. % and after that from 2 to 6 wt. %. In addition, the nodularity of graphite increased with the increment of the aluminum amounts. By adding the amount of copper, the surface fraction and nodule count of graphite increased and nodularity of graphite decreased. The addition of aluminum and copper decreased the surface fraction of ferrite and increased the surface fraction of pearlite in the microstructure. By increasing the amounts of aluminum and copper, compressive stress vs. strain curves were shifted upwards, and modulus of elasticity, yield strength, maximum compressive stress, and fracture strain improved. In comparison with copper, aluminum had a greater influence on the mechanical properties of ductile iron.