What is hard metal?
Hard metal (widia – the name comes from the German phrase wie Diamant, “like diamond”) is a composite material. Composite materials consist of two or more metals which are not mutually dissolving, even in liquid form, or of a mixture of metals and non-metallic components such as oxides, borides, nitrides, and other high melting point materials.
Composition
HM is produced of WC, giving a high hardness, and Co as the bonding phase, giving HM its toughness. Carbides TiC, TaC, NbC are also added to improve the properties of HM for a particular application (high hardness, resistance to high working temperatures). The selection of components and the technological process of obtaining HM defines its final properties, and thus the possibility of application.
Properties
HM’s superior properties in terms of hardness, wear resistance, strength, corrosion, and high temperature operation are due to the following physico-chemical properties: (Table 1)
Table 1: TM properties (exemplified by K-grade HM)
ISO
|
WC
% |
CO
% |
γ
g/cm3 |
HARDNESS
HV20 |
TOUGHNESS
N/mm2 |
STRUCTURE |
GRAIN SIZE WC
μm |
| K-10 |
94 |
6 |
15,0 |
1650 |
1500 |
fine |
1 |
| K-20 |
94 |
6 |
15,0 |
1550 |
1700 |
medium |
1,5 |
| K-30 |
91 |
9 |
14,6 |
1500 |
2000 |
medium coarse
|
2,5 |
Methods of obtaining TM
HM is produced by means of
powder metallurgy. The process involves the production of metals in powder form and their processing by
sintering.
Basic operations in the production of HM are:
- Mixing metal powders with each other and with a suitable lubricant.
- Pressing, i.e. loading the mixture into suitable die to apply pressure, producing pressings of a specific density and strength.
- Sintering, i.e. heat treatment of the compact in a protective atmosphere at a temperature below the melting point of the main components (1400 °C), where the powder particles are tightly linked, eliminating the hollow phase (pores) and reaching almost its theoretical density, thereby gaining the requested properties and dimensions (which are now reduced by ~ 20% compared to the dimensions of the molded parts/pressings).
Application area
Because of its properties HM is used for:
- Metal processing
- Rock and stone processing tools
- Wear-resistant structural parts
- ...
Alfa Tim manufactures HM for the following purposes:
- processing all types of metal by turning and milling, for all types of processing - fine, medium and coarse
- processing of non-metals, plastics, ceramics
- processing of ferrous metals
- wood processing
- stone processing
- mining industry applications
- civil engineering applications
- special products
Selection of HM grade and product form are made according to customer demand.