Friction and wear behaviour of MoS2, boric acid, graphite and TiO2 at four different sliding speeds (1. 0, 1. 5, 2. 0, 2. 5 m/s) has been compared with dry sliding condition. MoS2 and graphite show 30 to 50% reduction in mass loss compared to other lubricants at all sliding speeds. Friction coefficient reduces with increase in sliding speeds for all the conditions. Friction coefficient of dry as well as lubricant coated samples varies from 0. 2 to 0. 55 with MoS2 showing the lowest value (0. 2). Boric acid and TiO2 coated samples show high friction coefficients at higher sliding speeds due to poor lubricity and adherence. This could also be due to sliding resistance offered by lubricant coated samples with predominant asperities interaction. MoS2 and graphite coated samples also generated lowest frictional temperature compared to other conditions. © 2012 Indian Academy of Sciences.

M. Kamaraj

Department of Metallurgical and Materials Engineering

BORIC ACIDS

Boundary lubrications

COATED SAMPLE

DRY SLIDING

FRICTION AND WEAR

Friction coefficients

FRICTIONAL TEMPERATURE

GRAY CAST IRON

Mass loss

SLIDING RESISTANCE

SLIDING SPEED

Boride coatings

Graphite

Inorganic acids

Molybdenum compounds

Solid lubricants

Titanium dioxide

Wear of materials

Friction

Fulltext

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IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Sadhana - Academy Proceedings in Engineering Sciences

The austempering behavior of a series of hypereutectic alloyed gray iron compositions with carbon equivalent from 4.37 to 5.14 was studied to understand the influence of microstructure on its mechanical and wear properties. The alloying elements in the alloys included Ni, Mo, Cr and inoculation by micro-constitution of Ti, Nb and Ce. The alloys were austempered at 360 °C and upper bainitic type feathery ferrite was observed in the matrix. While the graphite content determined by optical metallography varied between 16 and 24 vol%. The volume of austenite determined by XRD analysis showed values between 20 and 26%. The ferrite lath size was determined using XRD peak broadening. The tensile property varying between 188 and 270 MPa, showed no significant variation with volume percentage of carbon or austenite in the ausferrite. However the wear rate varying between 0.5 and 2.6 × 10-7 g/Nm, showed a decreasing trend with graphite content attributed to the higher lubricating effect of released carbon during sliding wear. The specific wear rate of hypereutectic alloys, increased with increasing ferrite lath size due to enhanced softer ferrite phase on the sliding surface. The wear rate was found to increase with volume of austenite, austenite carbon content and austenite lattice parameter, which is attributed to increased stability of austenite against strain induced martensite formation and the increased formation of bainitic carbides in the second stage tempering. The various technical aspects in correlating the microstructure with the mechanical and wear properties of hypereutectic austempered gray iron are described. © 2009 Elsevier B.V. All rights reserved.

Materials Science and Engineering A

Structure-property correlation in austempered alloyed hypereutectic gray cast irons

A high-strength and wear-resistant alloyed gray iron with ausferritic microstructure on solidification directly from molten condition could be made in a Ni and Mo alloyed gray cast iron. The as-cast ausferritic cast iron was compared with two conventionally austempered gray iron with and without Ni and Mo additions. The various phase constitution and volume fractions were analyzed using optical, SEM and XRD analyses. The various aspects of the alloy chemistry and processing conditions have been correlated with the microstructure and mechanical properties obtained. The analysis showed that the Ni-Mo alloyed austempered gray iron and the directly as-cast austempered gray iron had similar phase constitutions. The strength of the direct as-cast alloy with ausferritic microstructure was higher than the others due to its higher austenite content and carbide distribution. The wear rate of the conventionally austempered Ni and Mo containing alloy and direct as-cast ausferritic alloys is 20% of the austempered gray iron without Ni and Mo with friction coefficient less than 0.4. © ASM International.

Journal of Materials Engineering and Performance

Structure and property studies on austempered and as-cast ausferritic gray cast irons

Alloyed gray cast iron of varying compositions was studied for their wear behavior. In general, the alloyed gray irons studied have higher graphite volume fraction (∼20%) with Type-A graphite flake morphology. Base cast iron showed two to three times higher wear rates than the alloyed gray irons. Tensile strength and wear rates show decreasing trend with increase in graphite and carbide volume fraction. Wear track analysis shows three body abrasive wear mode resulting in debris generation and smudging along the wear tracks. The graphite gets released during sliding to form films along the wear tracks and then forms irregular debris. © 2009 Elsevier Ltd. All rights reserved.

Tribology International

Wear behavior of alloyed hypereutectic gray cast iron

The mechanical and wear behavior of a series of as-cast gray iron alloys were compared with properties obtained after austempering at 360 °C. The austempered alloys showed equivalent or moderately enhanced mechanical strength than the as-cast pearlitic gray irons. The specific wear rates of all the austempered alloys decreased significantly by 7-15 times and friction coefficient reduced by 30-50% compared to pearlitic alloyed gray irons. The dry sliding wear studies of as-cast alloys against high carbon 1%Cr through-thickness hardened steel shows that the specific wear rate ranged from 5.6 to 19.1 (×10-7) g/Nm with friction coefficient from 0.55 to 0.7. While, the austempered alloys showed wear rates from 0.5 to 2.6 (×10-7) g/Nm with friction coefficient ranging from 0.23 to 0.4. The improved wear resistance was attributed to the layer wise surface phase transformation associated with strain induced martensite formation of the stabilized austenite in the austempered matrix, lubrication of the interface by the flake graphite and better heat conduction from the rubbing interface by higher volume fraction of the graphite. Cast iron alloyed with Ni shows enhanced mechanical properties and wear resistance. The tensile strength shows decreasing trend with increase in carbon equivalent and graphite volume. The specific wear rate and friction coefficient shows decreasing trend with increase in hardness and graphite flake volume. © 2009 Elsevier Ltd. All rights reserved.

Materials and Design

Studies on mechanical and wear properties of alloyed hypereutectic gray cast irons in the as-cast pearlitic and austempered conditions

Alloyed grey cast iron is an important automotive material used in clutch and brake applications. In order to understand the influence of microalloying additives on the graphitic morphology, mechanical and wear behaviour, a series of microalloyed cast iron melts were taken. The laboratory scale ingots made were characterised for microstructure, mechanical properties and wear behaviour. All the cast irons made were hypereutectic with a microstructure consisting of class A type graphite in a pearlitic matrix with eutectic grain boundary carbides. The microalloyed cast irons showed two- to threefold improved wear resistance over a base unalloyed material at comparable mechanical strengths. The wear loss was found to be linear with increasing sliding distance, and the wear resistance is attributed to the combined influence of dense pearlitic matrix with carbides and good distribution of graphite flakes. Cast iron microalloyed with Ni (0.62%) with Ce inoculation showed best overall properties compared to other alloys. © 2010 Maney Publishing.

Materials Science and Technology

Mechanical and wear behaviour of alloyed hypereutectic grey cast iron

Effect of solid lubricants on friction and wear behaviour of alloyed gray cast iron

Journal	Sadhana - Academy Proceedings in Engineering Sciences
ISSN	02562499
Open Access	Yes