Preventing cracking in tungsten carbide
Cracking in brazed tungsten carbide components
This is not an uncommon issue and can occur due to:
- Stresses that arise in the brazed assembly due to contraction during the cooling of the joint from brazing temperature.
- Changes in stress-levels that will arise when the brazed assembly is subsequently machined to its final shape.
- Percussive, thermal or other stress shocks that the assembly will experience in service.
Managing stress in brazed tungsten carbide joints
Managing these stresses is the key to avoiding cracking in tungsten carbide and this is often a detailed issue to address successfully. VBC Group is able to provide in-depth technical support in this area. The following points need to be assessed and if necessary addressed:
Joint design – avoiding points where stress can concentrate or build up.
Alloy selection – selecting an alloy or product form that helps to reduce stress build-up, absorb stress or cushion the joint in service. In general:
- Meta-Braze™ 155 and Meta-Braze™ 156 are suitable for brazing small tungsten carbide tips of <10mm on the longest dimension.
- Meta-Braze™ 449 and Meta-Braze™ 450 are recommended for brazing medium sized tungsten carbide tips of 10-20mm on the longest dimension. These alloys are also suitable to use on larger carbide segments where Trifoil isn’t an option due to the joint geometry.
- Meta-Braze™ 049 Trifoil and Meta-Braze™ 450 Trifoil are recommended for brazing larger tungsten carbide segments of >20mm on the longest dimension. These products are also suitable to use on components which will see percussive impact or high stress shocks in service.
Heating and cooling – even heating and slow cooling can help reduce the stress or thermal shock that a component will be subjected to.
Post-braze operations – need to be carefully controlled.
Service conditions – cracking may be inevitable in certain extreme or arduous applications. Braze alloys should be selected to withstand the service conditions if possible.
Contact VBC Group or speak to one of our technical specialists for more information.