Every Hardfacing process has its own deposition quality limitation. Processes like TIG-Hot wire, PTA and Laser can produce high quality results, on the other hand they bring together high operational costs. These costs are especially due to the low deposition rate, high equipment investment and higher operational complexity.
A good alternative to lower the Hardfacing costs is suiting less complex and low-cost processes, like GMAW, to this kind of operation. With the right parameterization and adaptations to its process, it is possible to achieve high quality deposition, relatively close to PTA and LASER ones.
We can qualitatively measure the deposition metallurgical result in three main aspects:
Dilution control and deposit thickness;
Preservation of deposited materials;
Number of defects and discontinuities (porosity, lack of fusion, spatter).
The high quality achieved by the advanced processes previously cited is given mainly due its inherent better energy input and metal transfer control. This, in certain way, prevents the increment of deposition rates. It’s seen then a kind of seesaw of gains and losses: the higher the quality achieved, harder it is to improve the resultant deposition. Similarly, when we try to increase the deposition rate there will be a loss in quality.
So how to overcome this limit and improve the global efficiency?
A solution is the advanced GMAW processes, like, per example, the imposition of alternating current or the simultaneously feeding of two or more wires. These varieties can keep the conventional deposition rates and at the same time improve the energy input control, allowing a far better deposition quality. Although these processes are more complex than the traditional version, they are still humbler and less costly than PTA and LASER.
Another solution is the consumables improvement, as the use of special flux-cored wires with higher quality control, what can decrease significantly the number of defects and discontinuities of the welding. Per examples, the use of micro alloyed flux-cored wires filled with tailormade powder composition, specifically for the accuracies of the process. Even though the price is higher it can reduce dramatically the post work due to defects, decrease the material loss due to spatter and slag formation.
Although the coating quality achieved by PTA and LASER process are far superior, the results from advanced GMAW are extremely distinguished from the traditional GMAW. This difference opens a new application niche, once it’s cost benefit ratio lies in a gap still not well explored by the industry.
The technology is in our favor and those who do not update their processes run the risk of being left behind!
Learn more about the Hardfacing coating process through the article Hardfacing: Overcoming Wear
We thank Eng. Pedro Jeager for the valuable technical contribution in co-authoring the article.
Reference: P. C. R., Jaeger, A new solution for wear and corrosion protection: alternating current MIG welding process with nickel, cobalt and iron basis flux-cored Hardfacing wires.