What is Hardfacing?
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Before we jump to the techniques and process of hardfacing welding, let us primarily understand what does hardfacing welding mean. Hardfacing welding technique is used to make equipment more efficient by minimizing oxidation and distortion, resistance from chipping and corrosion. This process is cost-efficient compared to buying completely new equipment to replace the worn-out one. How is that?
Hardfacing a machine involves putting a tougher, harder material onto the base metal to increase its lifespan. Generally, hardfacing takes the form of specialized hardfacing electrodes for MIG welding or arc welding. This is a fast and easy method that also helps reduce the number of spare parts kept in the inventory.
Significant reduction in production cost and lessened machine downtime is the key reason why the use of hardfacing machines has become popular in food, petrochemical, mining, power, cement, sugarcane and steel industries. Using the hardfacing technique can make new machines resistant and lengthen their life by up to 300%. When used on old equipment, hardfacing can return worn parts to nearly new condition at 25-75% less cost than that incurred on replacement of those parts.
What materials can be applied in the hardfacing process?
No matter the industry in which a machine is used, there is a specified hardfacing welding electrode that can be appropriately used to offer maximum resistance to wear and erosion. The common materials, however, used widely across all industries include NOREM, chromium carbide alloys, stellite or cobalt-based alloys and nickel-based alloys. Carbide or chromium carbide alloys are generally used in case of low-stress scratching on machines. Here the wear is very minimal and can be caused by scouring actions of materials around the equipment. In case if you wish to add your band name or additional information or need to add color to refine the work, hot stamping can be used post hardfacing. Most commercial industries make use of films or foils to add an additional layer of protection and/or to give the machine a metallic effect.
What steps one should follow before hardfacing a machine?
Yes, the problem at hand is a worn-out machine and the immediately required step is to get it hardfaced. But before you do that, make sure you follow these steps:
Clean the machine and especially the parts to be hardfaced very well
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Wipe it free of all contaminants such as grease, dirt, oil, or rust.
If necessary, remove the old hardfacing layers and/or cracks by using the arc or plasma gouging technique.
The size, shape and location of the equipment or its parts will determine the welding technique to be used while hardfacing. So make sure you keep that in mind.
Hardfacing most commonly makes use of the stick welding (SMAW) process as it is highly portable or the flux-cored (FCAW) welding technique. For welding large and thicker parts on regular basis, companies also make use of the submerged arc welding (SAW) process.
With this, your machine is prepped to be hardfaced and become more efficient.
Conclusion:
Hardfacing is a valuable technique that can help save your expenditure and time too. If you wish to know more about welding and everything around it, we are here to help you. The world of welding can be a little complicated but taking your time to learn the processes goes a long way.
Hardfacing is a surface processing technique which allows the production of functionally graded components for extreme wear, impact, corrosion, or temperature resistance application [ 1 ]. It is a cost-effective process where dissimilar surface layer(s) with unique properties are deposited onto the surface of used or new metal components to improve their service life while also reducing and/or preventing the breakdown cost for industries. Hardfacing can be applied to complex shapes and geometries or to specific areas of both worn and new metal components. A typical hardfacing deposition process is shown in Figure 1
3,4,5,8,9,The practice of hardfacing has been a longstanding concept since World War II [ 2 ]. The concept was initially developed to improve the surface hardness of mining components to provide better wear resistance and reduce the downtime and maintenance costs. More recently, hardfacing has been widely applied as a surface improvement technique by various industries, including agriculture, nuclear plants, construction, manufacturing, and railways. Earlier studies on hardfacing suggest that this technique is prominently and widely used by industries, especially to improve various types of wear performance, like abrasion, galling, and erosion [ 1 6 ]. Likewise, improving a component's resistance to impact and corrosion are other significant industrial applications of hardfacing. A few studies also show that this surfacing technique has potential in improving performance for kinetic projectile piercing [ 7 10 ].
Any hardfacing approach is primarily dependent on the intended application, which governs the selection of hardfacing consumables, substrate, and deposition process. The parallel development of areas, like material, manufacturing, and automation, is advancing and adding new materials, processes, and technologies that can be used for hardfacing. Thus, the selection of hardfacing alloys and deposition processes can be quite complex and requires proper understanding of the application requirements and operating conditions of the hardfacing product. Furthermore, several issues, including residual stress-induced cracking, spattering, distortion, fusion problems, dimensional inaccuracies, and dilution may be encountered during hardfacing deposition. Exacting standards are required to avoid or reduce these issues, optimise the process, and ensure the acceptable quality.
The objective of this paper is to conduct a thorough review of hardfacing research articles to summarise the criteria essential for performing hardfacing deposition for improving the quality, precision, and application requirement. This paper also seeks to highlight the factors influencing the general hardfacing practices and discusses associated hardfacing challenges to identify research gaps that are particularly important for improving the surfacing quality and advancing new areas of hardfacing application. The hardfacing approach is primarily dependent on the intended application, which governs the selection of hardfacing consumables, substrate, and deposition process. The parallel development of areas, like material, manufacturing, and automation is advancing and adding new materials, processes, and technologies that can be employed for hardfacing. We have hypothesised that the progress and understanding developed so far in hardfacing, along with the parallel development in the areas of materials and manufacturing technologies, can be utilised in hardfacing practices to address prevailing challenges, such as crack formation, thermal impact on parent metal, and residual distribution to improve the characteristics of the surfacing and to explore opportunities beyond conventional applications of hardfacing.
The contents of this paper are structured and presented according to the aforementioned objectives. Section 2 provides a concise overview of the methodology used to generate this paper. In Section 3 , the background information and understanding of the selection criteria of hardfacing processes and materials are presented. The selection of hardfacing alloys and deposition processes can be quite complex and requires proper understanding of the application requirements and operating conditions of the hardfacing products. Section 4 discusses the variables that requires consideration and optimisation during hardfacing, as they influence the deposition process and quality. Challenges, such as residual stress-induced cracking, distortion, surfacing hardened steels and dilution in hardfacing practices, are discussed in Section 5 to reflect potential aspects for future hardfacing studies. Section 6 highlights various hardfacing literature under different research themes and applications to provide an overview of the distribution of research focus across different areas and to help identify less explored areas. Finally, Section 7 concludes this paper and offers recommendations for potential future works based on the author's review.
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