Advances in Carbidic Austempered Ductile Iron (CADI) – a wear resistant material

Background: Ductile irons provide a more viable alternative for malleable cast iron in areas that do not demand extreme wear resistance. Austempering of ductile irons was a well researched area in the last two decades. Attempts to further improve the wear resistance led to the development of Carbidic austempered ductile iron (CADI), wherein the carbides contribute to wear resistance. Combination of ausferritic matrix, graphite nodules, and carbides (eutectic and alloy) symbolizes the microstructure of CADI. Methods: Two principal approaches adopted by the researchers to change the microstructure are (i) addition of carbide forming elements (ii) heat treatment (s). Results: Both the above methods result in the refinement of graphite nodules, carbide precipitations, along with fine ausferrite. Conclusion: Improvement in hardness, toughness and wear resistance was observed largely as a consequence of fine carbide precipitations and formation of martensite.

High-Speed Steel Surface Modification by Electron-Beam Processing

The structure and microhardness of high-speed steels P6M5, P9 and P18 after electron-beam processing were investigated in the work. Electron-beam processing was carried out on the industrial accelerator ELV-4. It was established that electron-beam processing allows to obtain a modified layer on the surface of fast-cutting steels with thickness of 20 μm with high hardness, consisting of fragmented martensite with fine carbide particles. It was determined that after electron beam processing the microhardness of high-speed steels increased to 9.5 GPa. It has been experimentally established that the growth of hardness and wear resistance of high-speed steels after electron-beam processing is the result of the formation of more fragmented martensite and a decrease in the size of carbide particles.

Welding Consumables for 2.25Cr-1Mo-V Refining Reactors

Owing to the demands for larger-capacity reactor vessels in petroleum plants and higher temperature processes for the upgrade of heavy oil, enhanced 2.25Cr-1Mo, 2.25Cr-1Mo-V and 3Cr-1Mo-V steels, which suit both high temperatures and pressure operations, have been developed and used for heavy-wall pressure vessels since the 1990s. 2.25Cr-1Mo-V steel, which has very special mechanical properties, resistant to both hydrogen attack and embrittlement under high temperatures and pressure environments in particular, has been used since 2000. The specifications for 2.25Cr-1Mo-V steel pressure vessels, such as ASME Sec. VIII and API RP 934-A, have been established and reviewed to enhance the contents [1–2]. In this report, the transition of materials, the welding techniques for hydrocracking reactors and 2.25Cr-1Mo-V welding materials are introduced. Particularly, for these welding materials, in order to improve the creep rupture and temper embrittlement properties, the effectiveness of precipitates is discussed. It was found that fine carbide (MC) in crystal grains improves creep rupture lifetime and MC at the prior austenite (γ) grain boundaries inhibits temper embrittlement caused by the segregation of impurities.

Effect of Finishing Techniques on the Junction Between the Composite Restoration and the Dental Enamel

The aim of this in vitro study was to to evaluate the impact of finishing procedures on the enamel adjacent to composite restorations and to assess if the resistance of the enamel-resin junction to leakage is affected by the use of these instruments. The surfaces of enamel at the joint with composite were observed by scanning electron microscopy, then the microleakages at the enamel margin was assessed using an optical microscope. Finishing with extra-/ ultra-fine carbide burs and extra-fine diamond burs produced a superficial abrasion to the adjacent enamel and did not seem to have a significant influence on the sealing ability of composite resin.

CARPENTER CTS 20HC ALLOY

Carpenter CTS 20HC is a version of type 420 martensitic stainless steel containing nominal 0.5% carbon content. The chemical composition and processing of CTS 20HC have been tailored to provide a uniform, fine carbide structure that can be considered for the manufacture of thin sections and fine blanking operations. This alloy can achieve a tempered hardness capability of HRC 55. This datasheet provides information on composition, physical properties, and tensile properties. It also includes information on corrosion and wear resistance as well as forming, heat treating, and machining. Filing Code: SS-1188. Producer or source: Carpenter Specialty Alloys.

CARPENTER CTS BDZ1 ALLOY

Carpenter CTS BDZ1 alloy is a martensitic steel chemically balanced and processed to provide a uniform, fine carbide structure. This structure has been suitable for the manufacture of thin sections and fine blanking operations. This datasheet provides information on composition, physical properties, and hardness. It also includes information on corrosion and wear resistance as well as forming, heat treating, and machining. Filing Code: SS-1185. Producer or source: Carpenter Specialty Alloys.

Investigation on the Austenizing Transformation Process in Continuously Heated X65 Microalloyed Pipeline Steels

Austenization is an important stage during the quenching-tempering heat-treatment process of X65 microalloyed pipeline steel, because it can influence the development of final microstructure and mechanical properties. In this paper, a detailed investigation was carried out on the austenizing transformation process in X65 microalloyed pipeline steel using high-resolution dilatometric technique and microstructure observations. According to the obtained dilatometric curve during continuous heating, the austenizing transformation process in X65 steel was apparently composed of two stages, 740-765°C and 765-875°C respectively. In order to clarify the microstructure evolution during the two stages, interrupt heat treatment tests were performed and subsequent microstructural observations showed that the first stage (740-765°C) was corresponding to the dissolution of fine carbides particles and the second stage (765-875°C) was corresponding to αγ phase transformation. Firstly, austenite nucleates at interfaces between fine carbide particles and ferrite matrix due to the high interface energy there and then the carbide particles dissolve into the austenite nucleus, which constitutes the first stage. After the fine carbide particles dissolve completely into the austenite nucleus, the ferrite matrix relatively far from the original carbide particles needs higher thermal driving force to transform to austenite, therefore the major αγ transformation occurs at higher temperature range (the second stage).