Pump sleeves have proven to be an effective application of the boriding technology by dramatically increasing the wear resistance of the sleeve exterior. Typically, pumps see very high wear on pump sleeves and this necessitates using expensive coatings such as thermal spray to combat the wear action. Hard chrome is also often used.
But these coatings can suffer from adhesion failure where delamination or chipping can occur. Also sub-layer corrosion from porosity or cracks in the coating can cause delamination to occur leading to a sharp and deep scar that quickly slices the seal packing and requires immediate replacement. Also both of these processes require complicated (read: expensive) machining or grinding before – and after – coating which adds to the costs associated with these coatings.
In contrast, Borided pump sleeves can be made from conventional hollow bar material such as ST52, machined to the final size and surface finished before processing. Boriding converts the surface to ceramic iron boride which diffuses more than 0.2 mm into the surface of the sleeve with a hardness of over 75 HRc. Due to the saw-tooth like diffusion pattern, chipping and delamination is basically eliminated. Boriding is a simple, high performance, cost effective process.
We have also embarked on an extensive research programme to optimize the Boriding process and we are now able to deep-case boride the sleeves for extended life.
An overall better economy is achieved with regards to wear performance and at a reduced cost to both chrome and thermal spray.
The advantages of boriding for pump sleeves are the following:
- no complicated prepartion or finishing off of parts
- smooth, even wear with no delamination or release of hard particles
- boriding is a smooth, pore free coating and hence no corrosion initiation points.
- no under-coating corrosion at the coating/steel interface
- boriding is highly resistant to thermal shock
- Stainless steels, nicel based alloys and cobalt based alloys can also be treated with little or no corrosion resistance but with dramatic improvement in wear resistance.
For more information concerning your particular application, please contact us.