The major objective of this program is to reduce the current high maintenance costs in the mining and mineral processing industries which relate to the repair of fatigue cracking and the replacement of worn surfaces. This will be done by developing improved processes for surfacing of high wear parts and by developing more resistant overlays which address more than one wear mechanism.

The first stage towards the achievement of this objective will be the completion of the following projects:

Corrosion/erosion/abrasion behaviour of hardfacing deposits
Chromium-bearing white iron hardfacing deposits are extensively used in mining, quarrying and mineral processing industries. These alloys are characterised by the presence of two distinct phases ie an iron-chromium-carbon austenite matrix and reinforcing iron-chromium carbides. Resistance to wear by abrasion, erosion and corrosion depends on the properties of both the matrix and the carbide network. The chromium content of the iron-chromium carbides is higher than that of the austenite matrix. The implication is that the formation of carbides, which are necessary for resistance to abrasion or erosion, depletes the matrix of chromium thereby compromising resistance to corrosion.

With respect to corrosion, it has been shown that the behaviour of hypoeutectic deposits (low carbide volume fraction) is quite different from that of hypereutectic deposits (high carbide volume fraction). The behaviour of both types of deposit is more complex than for a typical engineering material. The role of chromium in conferring corrosion resistance has been reassessed. In laboratory tests, it was shown that the iron-chromium carbides may be susceptible to corrosion under certain electrochemical conditions in aqueous media. It also appears that there could be an optimum carbide volume fraction under conditions of erosion-corrosion. These results have significant implications for mineral processing industries that rely on high volume fractions of carbides to achieve acceptable erosion or abrasion resistance.

Robotic gas metal arc welding
The goal of this project is to develop a fully automatic robotic gas metal arc welding cell capable of performing rapid prototyping and wear replacement. Rapid prototyping is the fast manufacture of prototypes of machine parts or components that allows prototypes of newly designed objects to be produced in a fraction of the time it would take to produce them in the traditional manner. Rapid prototyping by gas metal arc welding is relatively new and has the advantage of being able to produce fully functional metal components. Wear replacement is the repair of worn machinery by depositing successive layers of weld metal on top of the worn part in order to build it up to its original shape in order to save on the cost of replacement. Wear replacement has long been performed manually but cost and especially safety concerns warrant the development of an automated system.

An advanced, fully integrated computer-controlled robotic gas metal arc welding cell has been successfully set up comprising a latest generation ABB IRB1400 S4C robot, interfaced with a state-of-the-art Lincoln Power Wave 450 synergic welding power supply, and a PC. A methodology has been developed by which automatic robotic rapid prototyping and wear replacement can be performed. A weld monitoring system was installed which can monitor the welding voltage, current, wire feed speed and the shielding gas flow at high speed and transfer the acquired data to the PC for either real-time quality control or for post-weld analysis. An ethernet connection was set up between the PC and the robot through which they can communicate, and various pieces of software have been successfully written for the PC that can monitor and control all aspects of the robot's functionality. Also, a computer program has been written that can automatically convert path information from AutoCAD output into a robot welding program, as well as automatically transfer the robot program file to the robot and instruct the robot to execute it. Finally a surface scanning system has been built for the welding cell that uses a mechanical scanner, the robot and a program written for the PC to scan the surface of an object. The main task currently being undertaken is the development of algorithms that can automatically generate weld paths out of drawing data for solid and thin walled objects under any conditions.