Grain size

A material's grain size is important as it affects its mechanical properties. In most materials, a refined grain structure gives enhanced toughness properties and alloying elements are deliberately added during the steel-making process to assist in grain refinement.

Grain Size of single-phase metals and alloys is determined by the following methods

	Comparison method
	Planimetric (or Jeffries’) method
	Lineal intercept (or Heyn) method
	Intercept open scale (Snyder and Graff) method

Grain Size Determination of metals and alloys is carried out as per IS 4748 & ASTME 112.

Effective Case Depth

Measurement of effective case depth is used to determine the depth to which the micro indentation hardness of the exterior portion of a part has been increased over that of the interior of the part.

Non-metallic inclusion content

Non-metallic inclusions are chemical compounds of metal with non-metal which are present in steels and alloys like separated parts.

These are oxides, sulphides, nitrides and phosphides of iron, manganese, chromium, silicon, magnesium and other elements. The content of non-metallic inclusions should be kept to a minimum and not more than 2%.

Non-metallic inclusions in steel are undesirable substances. They disrupt the homogeneity of structure, so their influence on the mechanical and other properties can be considerable. During deformation which occur in the process of flattening, forging and stamping non-metallic inclusions can lead to cracks and to fatigue failure of steel.

The presence of inclusions in a material can be used to determine the rolling direction of a plate. Three mutually perpendicular axes are polished and examined. Inclusion stringer direction can be used to assess the direction of rolling.

Assessment of type, shape, quantity and distribution of inclusions is done as per IS 4163-2004 and ASTM E45.

Segregation of Carbides

Carbide segregation to the prior boundaries of particles used in powder metallurgy to generate an article is eliminated through the use of a nickel-base alloy powder which coordinates carbon with the amount of Mo and W which can form detrimental amounts of undesirable carbides and with Cb, Ta, Hf and Zr which are strong formers of a desirable MC-type carbide.