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Article

Sukru Taktak and Sinan Ulu

The purpose of this paper is to characterize carbide coatings obtained by thermo reactive diffusion (TRD) method on AISI 52100 and 440C bearing steels, which are…

Abstract

Purpose

The purpose of this paper is to characterize carbide coatings obtained by thermo reactive diffusion (TRD) method on AISI 52100 and 440C bearing steels, which are extensively used in industry, and to study wear behaviour of coated steels at elevated temperatures.

Design/methodology/approach

For coatings of vanadium and titanium carbides, TRD treatment is performed on AISI 52100 and 440C steels using pack method at 950°C for 3 h. Carbide coatings are characterized using X‐ray diffraction (XRD). The Daimler‐Benz Rockwell‐C adhesion test and micro‐Knoop indenter is used to assess the adhesion and hardness of the carbide layers, respectively. Ball‐on‐disc arrangement is used for determination of tribological properties of carbide‐coated steels. Friction and wear tests are carried out against Si3N4 ball at elevated temperatures up to 600°C under 5 N load, for sliding speed of 0.3 m/s.

Findings

The presence of carbides formed on AISI 52100 (Ti6C3.75 and VC0.88 phases) and on AISI 440C (Ti6C3.75, VC0.88 and minor Cr23C6 and Cr7C3 phases) is confirmed by XRD analysis. Hardness values of titanium and vanadium carbides on the 52100 and 440C steels are about 2,175‐2,464 and 2,128‐2,433 HK0.05, respectively. Friction experiments show that this type of coating is more effective than the substrates in regards to achieving lower friction up to 300°C. Above this temperature, the effect of substrate is more dominant on the friction coefficient. Scanning electron microscopy and energy‐dispersive X‐ray analysis results show the presence of the compact oxide layers at elevated temperatures as a result of increased sintering and oxidation of the wear debris.

Research limitations/implications

This paper deals with only characterization of vanadium and titanium carbide coatings and high temperature wear properties of the coated steels.

Practical implications

Carbide coatings obtained by TRD method are satisfactory in terms of high temperature tribological applications in comparison with those produced vapor deposition processes, which are expensive and complicated equipment.

Originality/value

There is no literature about high temperature wear and friction behaviour of TRD carbide‐coated 52100 and 440C steels. In this study, there are new results on high temperature wear of TRD carbide‐coated steels.

Details

Industrial Lubrication and Tribology, vol. 62 no. 1
Type: Research Article
ISSN: 0036-8792

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Article

Sam Joshy, Jayadevan K.R., Ramesh A. and Mahipal D.

The prime task of research in hot forging industry is to improve the service life of forging dies. The in-service microstructural changes that may occur in a die during…

Abstract

Purpose

The prime task of research in hot forging industry is to improve the service life of forging dies. The in-service microstructural changes that may occur in a die during hot forging is expected to significantly affect the service life. The purpose of this work is to analyse the microstructural evolution of double tempered hot forging dies in a real industrial environment, and the correlation of microstructural and microhardness evolution to the in-service wear and plastic deformation.

Design/methodology/approach

Specific hot forging tests were carried out on double tempered AISI H11 chromium tool steel for 100, 500 and 1,000 forging strokes. Macro analysis was conducted on die cross section to analyse the wear and plastic deformation at different stages of forging cycles. Microhardness and microstructural analyses were performed on the die surface after these forging tests.

Findings

The macro analysis on the transverse section of dies shows that wear is predominant during initial forging strokes, whereas plastic deformation is observed in later stages. Microstructural analyses demonstrate that during first 500 forging cycles, carbide population decreases at 63 per cent higher rate as compared to corresponding drop during 501 to 1,000 forging cycles. Additionally, the carbide size increases at all stages of forging cycle. Further, microstructural images from dies after 1,000 forging strokes show clustering and spherodisation of carbides by which the “blocky”-shaped carbides in pre-forging samples had spherodised to form “elongated spherical” structures.

Practical implications

The findings of this work can be used in hot forging industries to predict amount of wear and plastic deformation at different stages of service. From the results of this work, the service life of double tempered H11 hot forging dies used in forging without lubrication is within 501 to 1,000 forgings.

Originality/value

Most of the literatures are focussed on the cyclic softening of material at constant temperature. This work analyses the microstructural evolution of double tempered hot forging dies in a real industrial environment and correlates the microstructural and microhardness evolution to the in-service wear and plastic deformation.

Details

World Journal of Engineering, vol. 16 no. 5
Type: Research Article
ISSN: 1708-5284

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Article

X. Canute and M.C. Majumder

Aluminium metal matrix composites are used in automotive and aerospace industries because of their high performance and weight reduction benefits. The current…

Abstract

Purpose

Aluminium metal matrix composites are used in automotive and aerospace industries because of their high performance and weight reduction benefits. The current investigation aims to focus on the development of the stir cast aluminium-boron carbide composites with enhanced mechanical and tribological properties.

Design/methodology/approach

The aluminium-boron carbide composites are produced by stir casting process. Aluminium alloy A356 is chosen as the matrix material and three sets of composites are produced with different weight fractions of boron carbide particles. Higher particle size (63 µm) of boron carbide is chosen as the reinforcement material. Aluminium-boron carbide composites are tested for mechanical and tribological properties. The effect of process parameters like load, speed and percentage of reinforcement on the wear rate are studied using the pin-on-disc method. The interaction of the process parameters with the wear rate is analysed by DesignExpert software using RSM methodology and desirability analysis. The coded levels for parameters for independent variables used in the experimental design are arranged according to the central composite design. The worn surface of the pin is examined using a scanning electron microscope. The phases and reaction products of the composites are identified by X-ray diffraction (XRD) analysis.

Findings

Aluminium-boron carbide composites reveal better mechanical properties compared to monolithic aluminium alloys. Mechanical properties improved with the addition of strontium-based master alloy Al10Sr. The ultimate tensile strength, hardness and compressive strength increase with an increase in the reinforcement content. The wettability of the boron carbide particles in the matrix improved with the addition of potassium flurotitanate to the melt. Uniform dispersion of particles into the alloy during melting is facilitated by the addition of magnesium. Wear resistance is optimal at 8 per cent of boron carbide with a load 20 N and sliding speed of 348 RPM. The wear rate is optimized by the numerical optimization method using desirability analysis. The amount of wear is less in Al-B4C composites when compared to unreinforced aluminium alloy. The wear rate increases with an increase in load and decreases with the sliding speed. The wear resistance increases with an increase in the weight fraction of the boron carbide particles.

Practical implications

The produced Al-B4C composites can retain properties at high temperature. It is used in nuclear and automotive products owing its high specific strength and stiffness. The main applications are neutron absorbers, armour plates, high-performance bicycles, brake pads, sand blasting nozzles and pump seals.

Originality/value

Al/B4C composites have good potential in the development of wear-resistant products.

Details

Industrial Lubrication and Tribology, vol. 70 no. 2
Type: Research Article
ISSN: 0036-8792

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Article

Weishan Huang, Jing-Li Luo, Hani Henein and Josiah Jordan

This paper aims to evaluate the sulfide stress cracking (SSC) resistance of L80 casing steels with different alloying chemistries (e.g. Ti-B and Mn-Cr-Mo) by correlating…

Abstract

Purpose

This paper aims to evaluate the sulfide stress cracking (SSC) resistance of L80 casing steels with different alloying chemistries (e.g. Ti-B and Mn-Cr-Mo) by correlating the reduction in area ratio with the mechanical property, inclusion and carbide.

Design/methodology/approach

SSC tests were conducted in 5.0 Wt.% sodium chloride and 0.5 Wt.% acetic acid solution saturated with H2S using constant load tensile method. The microstructure and fracture morphology of the steel were observed using scanning electron microscope. The inclusion and carbide were identified by energy dispersive spectroscopy and auger electron microscope.

Findings

Among all the testing steels, electric resistance welding (ERW) L80-0.5Mo steel demonstrates the highest SSC resistance because of its appropriate mechanical properties, uniform microstructure and low inclusion content. The SSC resistance of L80 steels generally decreases with the rising yield strength. The fracture mode of steel with low SSC resistance is jointly dominated by transgranular and intergranular cracking, whereas that with high SSC resistance is mainly transgranular cracking. SSC is more sensitive to inclusions than carbides because the cracks are easier to be initiated from the elongated inclusions and oversized oxide inclusions, especially the inclusion clusters. Unlike the elongated carbide, globular carbide in the steel can reduce the negative effect on the SSC resistance. Especially, a uniform microstructure with fine globular carbides favors a significant improvement in SSC resistance through precluding the cracking propagation.

Originality/value

The paper provides the new insights into the improvement in SSC resistance of L80 casing steel for its application in H2S environment through optimizing its alloying compositions and microstructure.

Details

Anti-Corrosion Methods and Materials, vol. 66 no. 4
Type: Research Article
ISSN: 0003-5599

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Article

VAUN THOMAS

Cemented carbides are probably the most successful composite materials ever produced. They are best known for their outstanding wear resistance but many of their unusual…

Abstract

Cemented carbides are probably the most successful composite materials ever produced. They are best known for their outstanding wear resistance but many of their unusual properties remain largely unexploited. The author, Research and Development manager of Sandvik Hard Materials Ltd, Coventry, outlines the distinctive characteristics of this range of materials and illustrates their advantages in a wide field of engineering applications.

Details

Industrial Lubrication and Tribology, vol. 38 no. 4
Type: Research Article
ISSN: 0036-8792

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Article

Minghua Pang, Xiaojun Liu and Kun Liu

This study aims to clarify the influence mechanism of surface texture (arrays of circular/square and concave/convex) on the frictional properties of WC-TiC/Co cemented…

Abstract

Purpose

This study aims to clarify the influence mechanism of surface texture (arrays of circular/square and concave/convex) on the frictional properties of WC-TiC/Co cemented carbide under a water-miscible cutting fluid (JAEGER SW-105, 5 per cent) environment.

Design/methodology/approach

Four types of textured cemented carbide surfaces (arrays of circular/square and concave/convex that have different textured densities and sizes) were fabricated using laser surface technology. Pin-on-disc tests between an AISI 304 stainless steel ball and WC-TiC/Co cemented carbide samples were carried out for a variety of normal loads (1, 3 and 5 N) under a water-miscible cutting fluid environment. The effects of textured type, density and size on the friction coefficient were obtained.

Findings

Compared to a smooth surface, some textured samples successfully resulted in a reduced friction coefficient. The friction coefficient of textured WC-TiC/Co cemented carbide samples depended greatly on the textured type, density and size. Given the increase in textured density (ranging from 10 to 30 per cent), the friction coefficient of the test samples first decreased and then increased for all normal loads (1, 3 and 5 N), and the minimum friction coefficient was obtained at the textured density of 20 per cent. The concave textured surface showed obvious advantages in friction coefficient reduction regardless of textured density, size and normal load compared with the convex textured surface. Finally, the correlation between textured diameter/length and Hertzian contact width was studied for various normal loads and texture sizes. A 2.6 ratio of textured diameter/length to Hertzian contact width is recommended under for lubricated sliding contact with the water-miscible cutting fluid.

Originality/value

The main contribution of this work is in providing a design reference and obtaining an essential understanding on the effect of surface texture (arrays of circular/square and concave/convex) on the friction of WC-TiC/Co cemented carbide under a water-miscible cutting fluid environment.

Details

Industrial Lubrication and Tribology, vol. 70 no. 7
Type: Research Article
ISSN: 0036-8792

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Article

Cheekur Krishnamurthy Srinivasa, Chinnakurli Suryanarayana Ramesh and S.K. Prabhakar

The purpose of this paper is to study the effect of blending time, SiC content and fill ratio on the homogeneity of iron‐silicon carbide powder mixture, blended in…

Abstract

Purpose

The purpose of this paper is to study the effect of blending time, SiC content and fill ratio on the homogeneity of iron‐silicon carbide powder mixture, blended in double‐cone blender; to evaluate density, microstructure and micro hardness of laser sintered iron and iron‐SiC specimens; and study the feasibility of building a complex iron‐SiC metal matrix composite (MMC) part by direct metal laser sintering (DMLS) process.

Design/methodology/approach

The morphology and particle size of iron and silicon carbide powders were evaluated. Nickel coating was carried out on silicon carbide particles. Blending of iron‐SiC powders were carried out in two phases in a double‐cone blending equipment. In the first phase, three tests were conducted with fill ratios (ratio of volume of conical blender to volume of powder mixture) of 1.68, 3.39, and 6.8 percent while iron‐SiC weight ratio was kept constant at 97:3. In the second phase, four tests were conducted with iron‐SiC weight ratios of 99:1, 98:2, 97:3, and 95:5 while keeping a constant fill ratio of 1.68 percent. In both the phases, blending was carried out for duration of 43 minutes. Homogeneity of the powder mixture was evaluated at different intervals of time by adopting sampling process. Sintering was carried out on iron and iron‐SiC powder mixture using DMLS machine at laser speed of 50, 75, 100, and 125 mm/s. Microstructure, density and micro hardness studies were carried out on the sintered specimens. A 3D model of a part with complex geometry was modeled using Unigraphics CAD/CAM software and prototype part was built by DMLS technology using the blended iron‐2 weight percent SiC powder.

Findings

A reduction in blending time was observed with increase in SiC content and decrease in fill ratio. Microstructure and micro hardness tests conducted on laser sintered iron‐silicon carbide specimens, reveal the homogeneity of blended powder. The density of the iron‐SiC composites sintered at a laser speed of 50 and 75 mm/s, decreased with increase in SiC content. Further, an increase in the micro hardness of iron‐SiC composites was observed with increase in SiC content and decrease in laser speed. Complex functional part was built by DMLS technology with out any supports.

Research limitations/implications

The experiments were conducted with standard blending equipment in which the speed is limited to 48 revolutions per minute only.

Originality/value

Meager information is available on blending of powders for producing MMCs by laser sintering process. The work presented in this paper will be a guideline for researchers to carry out further work in blending of powders for producing MMCs by rapid prototyping process.

Details

Rapid Prototyping Journal, vol. 16 no. 4
Type: Research Article
ISSN: 1355-2546

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Article

James P. Hill

Has the public affairs function significantly changed the way major U.S. corporations meet the growing external challenge to traditional corporate practices? Examining in…

Abstract

Has the public affairs function significantly changed the way major U.S. corporations meet the growing external challenge to traditional corporate practices? Examining in detail the actions of Exxon (Valdez) and Union Carbide (Bhopal), this paper raises some questions as to whether the difference between public affairs and traditional public relations is a real one or merely a matter of semantics. Then, utilizing an unpublished corporate public affairs survey conducted by Central Michigan University, the writer argues that the problem with the public affairs function lies not with the function itself, but in its implementation by corporations.

Details

American Journal of Business, vol. 5 no. 2
Type: Research Article
ISSN: 1935-5181

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Article

Vladimír Čihal, Irena Kašová, Vladimír Masařik and Nadežda Lehká

ALLOYING with titanium transfers the steel into the passive state, lowering the critical passivation current density and, above all, increases the resistance to…

Abstract

ALLOYING with titanium transfers the steel into the passive state, lowering the critical passivation current density and, above all, increases the resistance to inter‐granular corrosion of welded joints in the critical temperature range, but a higher Ti content lowers the stability of the passive state and increases sensitivity to pitting corrosion by comparison with unstabilised steels. Adequate stabilisation ensures resistance to inter‐granular corrosion under the influence of critical temperatures, but stabilised steels are sensitive to inter‐granular corrosion in the overheated zone adjacent to the deposited metal of a welded joint, frequently to knife‐line corrosion even without the dual heating action of overheating to the solidus temperature and heating to critical temperatures during the application of a second weld layer or bead. Knife‐line attack is the result of heating the vicinity of a weld bead to temperatures close to the melting point, causing extensive dissolution of the Ti carbides, grain growth and an increase in ferrite content. During the subsequent action of critical temperatures (500–950°C) precipitation of Cr carbides, breakdown of ferrite, sigma‐phase formation, etc. occur which, jointly with the action of stress peaks in this zone, promote the tendency to knife‐line attack.

Details

Anti-Corrosion Methods and Materials, vol. 15 no. 11
Type: Research Article
ISSN: 0003-5599

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Article

Jonathan S. Kieman

THE introduction of tungsten carbide as a suitable material for precision gauge blocks began almost by accident.

Abstract

THE introduction of tungsten carbide as a suitable material for precision gauge blocks began almost by accident.

Details

Aircraft Engineering and Aerospace Technology, vol. 57 no. 9
Type: Research Article
ISSN: 0002-2667

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