Hardfacing Explained

What is Hardfacing?

Hardfacing is the deposition of hard wear resistant materials on worn or new component surfaces that are subject to wear in service. The abrasive and harsh nature of the mechanical processes of moving and transporting ores or dirt in the mining and construction industry often cause a lot of wear and tear to equipment and machinery, in fact enough to significantly reduce their lifetime and productivity. Metal parts in contact with mineral ores or soils often fail their intended lifespan not because they breakdown but because they wear too fast due to high abrasive nature and impact stresses which cause progressive deterioration.

Welding is an economic method used to apply hardfacing to improve the wear resistance of various components by the deposition of a hardfacing layer on the parts exposed to wear and tear. Welding a hardfacing protective layer or layers on components and tools subjected to aggressive wear is the most common industry method. However, there are other available methods.

Applying Hardfacing

Hardfacing is more than just applying a protective layer to a base material and hoping for the best… it is a process that needs careful consideration of all the applications parameters so you achieve the best outcome. Why spend countless hours on a cheaper 'multi-purpose' product that will barely provide double wear life? For any successful hardfacing outcome there is never one product that suits all. If there is a consistent environment provided, you must analyse the 'what, where, with and how' so you have the correct product to achieve the best outcome. The team at Jinhua are experienced in this area and are always ready to assist.

The prime factor to consider is whether it is an abrasion application or impact application, or even both? That's your starting point. Globally there are many manufacturers who will sell you anything just to get you to use their product and it may not necessarily be the right one. On the flip side however, there are manufacturers such as Jinhua that have excellent products designed for very specific applications.

Firstly, rebuilding may be required to restore the part to its original condition. This means that a filler has to be applied to bring the damaged worn part back to original state or to as near as possible. The filler material must have similar or uniform characteristics as the base, material compatibility is important as well for its success to eliminate the risk of cold cracking and provide a uniform operating temperature.

Buffer layer or layers need to be applied in some applications to overcome problems of incompatibility between substrate and cladding. It is designed to provide a good stable base between the parent metal and the hardfacing layer and avoid shrinkage cracks from the hardfacing to the base metal. Great care must be undertaken when choosing the filler metal for the buffer layer. If the differences in elasticity or expansion between the base metal, buffer and cladding are too great, this can cause the application to fail prematurely.

The top layer is the hardfacing layer and fundamentally if this is not harder than the parent metal, it will either not work, get torn off by impact or rapidly worn off by abrasion. This layer may involve depositing one or several layers of weld metal. Some hardfacing products are designed to be applied single layer only, while others can be applied as multiple layers. Factors of consideration are the environmental conditions, product toughness and resistance to impact or high temperatures and corrosion.

As well as rebuilding there is also preventive hardfacing where proactive hardfacing techniques are applied in the production of a brand new metal component or applied to equipment before it is used to preserve the integrity of the equipment and to minimise the need of rebuilding layer when replacing the hardfacing. In this case, the need for a buffer layer may also be less relevant.

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