Metal cladding techniques are often used to create an end product that has the necessary characteristics required for a specific application, for example, hardness to provide wear resistance.
Two or more layers of different metals are bonded tightly to each other. The combination of the contact material and the carrier are designed to provide the required resultant characteristics in the composite, unobtainable from a single metal.
A metal’s hardness is the characteristic that gives it strength and determines how yielding it is. Hardness can also refer to its stiffness, or temper, and resistance to cutting or abrasion.
There are several methods and scales used to measure metal hardness, including Rockwell, Brinell and Vickers. All are based on the resistance of the test piece to deformation using an indenter.
A fixed force or load is applied to the material sample and the indentation created is measured. Harder materials will yield smaller indentations; hence hardness measurement is calculated from the depth measured relative to the known load applied.
Here’s a quick summary of each technique, its uses, advantages and disadvantages:
The Rockwell method is a relative measurement of the net increase in impression depth as two known loads are applied. It uses a steel ball (Rockwell B Testing) or round-based, diamond-tipped cone (Rockwell C Testing).
Rockwell hardness testing is used:
- for measuring relative hardness
- on most materials, especially including harder plastics
The Rockwell hardness test:
- gives a direct read out of the test result
- provides comparison information
- is the most universally used
- is the most versatile test
However, the test
- cannot be used to assess material strength
- does not predict resistance to abrasion or wear
- should not be used, alone, for product design.
The Brinell method uses Meyer’s Law to assign a hardness index. An indentation is made by a steel carbide ball under a given load for a fixed length of time. This indentation is then examined optically and measured. The measurement is then converted to a Brinell value using specific formulae.
The ball diameter ranges from 1mm to 10mm and load from 1kgf up to 3000kgf. Impression time ranges from 10 to 15 seconds.
Brinell Hardness testing is used:
- most commonly for metals and alloys
- on larger parts, especially for forgings and castings
- to provide a reading of ultimate tensile strength
The Brinell Hardness test:
- is the oldest hardness test still in use today
- can be used on coarse material structures
- is effective on rough surfaces
- uses one scale to cover the entire hardness range
However, the test
- is slow to carry out
- may yield unclear results due to optical method of measurement
- results can vary greatly with small test variations and may be open to different interpretation
- makes comparison testing difficult
- requires surface preparation of the sample.
Vickers testing uses a square-based pyramid diamond indenter, with loads that can vary from grams to kilograms, according to the material being tested. Tiny indentations are measured optically and converted to a hardness measurement.
Vickers Hardness testing is used:
- on very thin materials and microstructures
- to measure surface depths
- to provide comparison readings for changes in hardness
The Vickers Hardness test:
- is good for small-sized samples
- produces extremely accurate readings
- can be used on soft or hard materials
- uses the same equipment for every test
However, the test
- involves expensive equipment
- requires preparation of the samples.
These different tests can give an indication of the hardness, or relative hardness, of a metal or alloy and this characteristic can be added to a composite material by using metal cladding services.
Vincent Metals use overlay or inlay cladding techniques to create sustainable custom composite solutions. Their in-house metallurgist and specialist materials engineering design team can help with every stage of the product development and manufacturing process. ISO Registered, Vincent Metals work only to the highest quality standards.
Whatever characteristics you need to achieve through metal cladding processes, contact Vincent Metal Corporation for expert assistance today.