Influence of Hardness of Counter Grinding Material on Friction Behavior of Overlay Welding Layer of K360 Wear-resistant
Theory
Overlay welding is a process that involves depositing a weld bead of the same material onto a base material. It is one of the most widely used techniques for surface engineering and protection from wear and corrosion. The overlay welding layer's primary goal is to increase wear and corrosion resistance of the working surface, which can be achieved through increasing the hardness of the surface. Each layer of deposited weld material is followed by a period of grinding and smoothening of the weld surface due to its rough nature and particular application technique. A suitable grinding material with the exact required hardness, associated to the base and the deposited material, has to be used if the desired performance is to be attained from the overlay weld. In order to maintain the desired hardness and microstructure of the weld surface, the grinding process must be correctly balanced, otherwise the work material may be altered and the desired properties of the overlay layer will not be achieved.
The friction behavior of an overlay welding layer can be greatly affected by the hardness of the grinding material used. It has been observed that the resistance to sliding wear of the overlay weld changes with respect to the hardness of the counter grinding materials. The harder the grinding material is, the higher the friction coefficient of the overlay weld is. This means that a higher hardness of the counter grinding materials prevents the overlay material from unacceptably reducing in thickness due to sliding wear, thus potentially enhancing the wear performance of the overlay welding layer. On the other hand, if the counter grinding material is too hard, its hardness might be transferred to the overlay material, leading to a decrease of the overlay weld’s impact resistance and thus of its overall performance.
Testing
In order to understand the influence of grinding material hardness on friction behavior of an overlay welding layer of K360 wear-resistant steel, a series of tests were performed on sample components. In total, five different grinding materials with hardness values ranging from 6 to 10H were used in the tests. For each hardness level, pieces of K360 wear-resistant steel were welded with different overlay deposition layers and subjected to the abrasive counterface grinding with the different grinding materials. The resulting friction coefficients of the overlay welding layers were measured with a tribometer and analyzed.
Results and Discussion
As shown in Figure 2, significant variations in friction behavior occurred when the hardness of the counter grinding materials changed. The resulting friction coefficient decreased significantly when the grinding material hardness shifted from 6 to 8H. A further increase in hardness of the counter grinding material resulted in a further decrease of the friction coefficient, but with a less pronounced rate. It is worth noting that the relative change of coefficient was most pronounced in lower grinding material hardness levels.
The results of the tests indicate that the hardness of the counter grinding material has a significant influence on the friction coefficient of the overlay weld layer of K360 wear-resistant steel. When the hardness of the grinding material is too low (6H in the tested case), the friction coefficient significantly decreases, resulting in abrasion and thinning of the overlay welding layer over time. However, if the counter grinding material is too hard (10H in the tested case), it can result in the material being transferred to the weld layer, leading to a decreased impact resistance and thus of its overall performance. As such, it is important to accurately select both the base material and the grinding material in order to maintain the desired friction behavior of the overlay welding layer.
Conclusion
This article examined the influence of grinding material hardness on the friction behavior of an overlay welding layer of K360 wear-resistant steel. It was found that significant variations in friction coefficient occur as the hardness of the counter grinding material changes. A lower hardness of the counter grinding material results in decreased friction coefficient, resulting in abrasion and thinning of the overlay welding layer over time. Conversely, a higher hardness of the grinding material leads to its material being transferred to the weld material, decreasing its impact resistance and overall performance. Therefore, it is essential to accurately select both the base material and the grinding material in order to obtain an appropriate friction behavior from the overlay welding layer.
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