Why is the outer surface of gear hard?

The idea behind case hardening is to keep the core of the tooth at a level which would not betoo much beyond 40 HRC,. to avoid tooth breakage, but to harden the outer surtace, or “case,” to increase pitting resistance. Of the methods for case hardening gears, carburizing isthe process which is most often used.

What hardness should gears be?

Typical gear tooth hardness after through hardening ranges from 32 to 48 HRC. Most steels that are used for through-hardened gears have medium carbon (0.3–0.6\%) and a relatively low alloy content (up to 3\%).

Is hardness a surface property?

INTRODUCTION. The hardness of the surface of components is an important property affecting their tribological performance. For components with non conformal contacts such as rolling bearings and gears, the hardness, and the corresponding compressive strength, of the surface material must be above a critical value.

What is hardness of a material and why is such an important material property?

Hardness is the property of a material that enables it to resist plastic deformation, penetration, indentation, and scratching. Therefore, hardness is important from an engineering standpoint because resistance to wear by either friction or erosion by steam, oil, and water generally increases with hardness.

Which surface hardening process gives maximum hardness to the surface?

Explanation: In surface hardness treatment, Nitriding gives the hardest surface.

Which of the following is surface hardening process?

To achieve these different properties, two general processes are used: 1) The chemical composition of the surface is altered, prior to or after quenching and tempering; the processes used include carburizing, nitriding, cyaniding, and carbonitriding; and 2) Only the surface layer is hardened by the heating and …

How can you increase surface hardness?

surface hardening, treatment of steel by heat or mechanical means to increase the hardness of the outer surface while the core remains relatively soft.

What is hardness property?

Hardness is the resistance of a material to localised plastic deformation. Hardness is just one mechanical measurement and properties such as toughness and strength need to be considered, as hard materials tend to have low toughness and can easily fracture. …

What is the difference between hardness and toughness?

Hardness: A material’s ability to withstand friction, essentially abrasion resistance, is known as hardness. Toughness: How well the material can resist fracturing when force is applied. Toughness requires strength as well as ductility, which allows a material to deform before fracturing.

What is toughness of a material?

Toughness is a fundamental material property measuring the ability of a material to absorb energy and withstand shock up to fracture; that is, the ability to absorb energy in the plastic range. Tough materials can absorb a considerable amount of energy before fracture, while brittle materials absorb very little.

Which process gives maximum hardness?

surface hardening process gives maximum hardness to the surface.

What is material hardness and hardness testing?

Material hardness and hardness testing. Material hardness is the property of the material which enables it to resist plastic deformation, usually by penetration or by indentation. The term of hardness is also referred to stiffness or temper, or to resistance to bending, scratching, abrasion, or cutting.

What is the relationship between hardness and wear rate?

If the hardness of the material is higher than that of the abrasive material, less wear rate will occur. Case hardening or surface hardening is the process in which hardness the surface (case) of an object is enhanced, while the inner core of the object remains elastic and tough.

Why is hardness important in Mechanical Engineering?

Hardness is important from an engineering standpoint because resistance to wear by either friction or erosion by steam, oil, and water generally increases with hardness. If the hardness of the material is higher than that of the abrasive material, less wear rate will occur.

How does hardness affect the resistance to deformation?

The greater the hardness of the material, the greater the resistance it has to deformation. Hardness has been variously defined as resistance to local penetration, scratching, machining, wear or abrasion, and yielding.