1.1 Mining Boom Cylinder Reclad & Repair

Road headers are flexible rock cutting machines widely used in mining, tunnelling and civil applications to cut soft to medium rock formations. The basic machine may be configured with a range of cutting heads to suit the application.

Within the boom a large diameter hollow hydraulic ram supports the rotating head, contains the driveline, and provides the thrust that keeps the cutters advancing into the rock face.

Damage to the hard chrome arises from impact abrasion and corrosion. Internal bearing surfaces wear with contamination of dust particles. This results in oil seal failure, machine downtime and lost productivity.

Laser cladding with advanced materials returned the ram to better than OEM standard at less cost.

Problem

• It is very difficult to protect the hard chrome surface of the ram from rock cuttings and fine abrasive particles. Impacts can dent the surface and chip the hard chrome.
• Hard chrome is a porous coating. In wet environments the moisture initiates rusting of the substrate steel, which results in delamination of the chrome coating.
• The nature of use often localises the wear into a narrow band.
• Internal driveline bearing surfaces wear and fail.
• Wear and damage to the ram surface damages oil seal. When damaged oil seals leak, performance deteriorates and oil is a pollutant.

Solution

• Hard chrome was machined from the damaged ram to prepare a clean substrate for subsequent laser cladding process. Internal machining prepares surface for cladding.
• Cladding material was selected to suit the application’s primary failure mechanism, in this case corrosion and impact resistance. Internal bearing surfaces were clad with different metallurgy.
• After laser cladding the ram was machined in high capacity lathes and borer machines to restore OEM dimensions.

Benefits

• Better than OEM surface metallurgy provides longer wear life.
• Road headers can be worked harder for longer.
• Less downtime and maintenance costs.

Feedback

Quality of rebuild provided us with a better than OEM component, which reduced our long-term unit operating costs.