Waterjet Cutter Nozzles By: Sarah Abatiello, Taylor Frederick, Luis Alzamora, Trevor Faber PRODUCT OVERVIEW The chosen product is waterjet cutter nozzles. These nozzles have specific material requirements due to the high pressure, abrasion, and corrosion that they endure. The first mechanical property that was identified as important is the toughness, since the nozzle will be repeatedly subjected to high water pressure (between 70-415 MPa) and abrasive impacts, and cannot fail. We are more concerned with toughness than just resilience because it is assumed that permanent deformation will occur and the nozzle will be replaced before it becomes detrimental to the cutting process. The upper part of the mixing chamber is the section that requires a higher toughness value, as that is where large angle impacts between the abrasive and the mixing tube occur (Hashish 1994). The next mechanical property of interest is the hardness, since the nozzle constantly has abrasive running through it during operation. The hardness of a material defines its ability to withstand any wear, erosion, or friction that will occur to the material overtime and during usage. When choosing a waterjet nozzle, the material in which it is made, needs to meet the standards for whatever it will be cutting and it will vary. In any circumstance, the water pressure running through the nozzle will create wear and eventually need replacing. The first thing to consider is if the waterjet will be using pure water or abrasive water. abrasive water consists of adding a material with the water to cut harder materials (Schlick). In this circumstance, the nozzle needs to have a relatively high hardness to withstand the abrasive water going through it. The most common abrasive used for water cutting is Garnet. Garnet has a hardness of 7.5-8.5 on the Mohs scale, therefore the nozzle needs to have a relatively similar hardness factor in order to function correctly without creating sharp edges in the cutting material, or slow down the cutting speed (What are garnet abrasives). Another factor to consider with the abrasive water is the pressure of the water running through the nozzle. The material used for the nozzle must have a high enough hardness to withstand the pressure flow of the abrasive, taking minimum damage to its functionality. To prevent minimum wear to the nozzle and the entire water jet, it is best to stay in the range of 40,000 psi- 60,000 psi for the water pressure (Schlick). Another material property to consider is corrosion resistance. This is beneficial because the nozzle has hard water running through it, so the minerals in the water can start to break down the nozzle material. Corrosion can also occur in areas of high mechanical wear, such as the mixing tube with high velocity abrasive running through it (Gök et al. 2023). Therefore it is important to choose a material with some corrosion resistance so the nozzle does not have to be replaced as frequently as if a corrosive material were to be used. MATERIALS CARBIDES Carbides are often used in the fabrication of water jet nozzles, specifically, tungsten carbide, boron carbide, tungsten carbide cobalt and a composite Carbide (ROCTEC 100) (Syazwani 2016). These materials are used because of the hardness and toughness properties, allowing them to resist wear and withstand pressure. The abrasion and erosion of tungsten carbide cobalt, boron carbide and composite carbide was tested in a research paper published by Ness and Zibbell (1996). The results above can be explained by observing the hardness and toughness of the carbide materials. Boron carbide which had the highest Hardness value of 9.5 on the Mohs scale had the largest resistance to erosion. However, tungsten carbide had the largest resistance to abrasion, likely due to its higher toughness compared to boron carbide. Despite Boron Carbide having the highest hardness and Tungsten Carbide being the toughest, the composite carbide ROCTEC 100 has the lowest wear rate due to its combination of toughness and hardness. During the test performed by Ness and Zibbell it was found that Boron Carbide also experiences cracking. This can be explained by its low fracture toughness compared to Tungsten Carbide and ROTEC 100. Increasing the toughness of Boron Carbide would make it the optimal carbide for water cutting nozzles. The primary contributor to the low fracture toughness are amorphous shear bands in the crystal structure that appear upon impact or under pressure (Shen et al. 2021). Through grain boundary engineering it is theoretically possible to increase the ductility of boron carbide. Reducing the difference in orientation between ordered regions will reduce grain sliding. This would likely be done by introducing additives into the material to reduce grain size (Shen et al. 2021). To conclude, unless strides can be made in increasing the ductility of boron carbide, ROCTEC 100 is the best overall choice for water jet cutting nozzles. If the water jet were to be only operated at lower pressures than boron, carbide would be the best choice because of its resistance to erosion. STAINLESS STEEL The arrangement of atoms forming into a unit cell of one or two more grains is called a phase. Certain alloy families are named after these phases. Austenitic, Ferritic, and Duplex are some commonly used terms to describe the type of phase a particular stainless steel is in. Yield Strength Hardness (Rockwell Test) Example Steel Austenitic 300 MPa 40-45 HRC 302 Ferritic 350 MPa 85 HRC 430 Duplex 650 MPa 48-56 HRC 420 Stainless This information is crucial in determining the suitable material for a water jet nozzle. The water jet operates under high pressure, and the material inside the nozzle must have a high yield strength. Without sufficient yield strength, the water within the nozzle could escape, resulting in uncontrolled high-pressure water release instead of precision cutting. The water jet's pressure ranges from 70 to 415 MPa, depending on the machine and the material being cut. For this reason, 420 stainless steel is the most reliable choice for the water jet nozzle. Hardness is another critical factor. The nozzle needs to resist deformation and scratching to ensure precise water delivery. Research indicates that a nozzle of this caliber should have a hardness of around 60 HRC. This makes 430 stainless steel a viable option. However, considering yield strength, 420 stainless steel remains the superior choice. This is why the ProtoMax employs 420 stainless steel. However 420 Stainless steel unfortunately is not the best material for corrosion under these conditions. A water jet nozzle is exposed to water and air for several hours each day, causing a pure 420 stainless steel water nozzle to corrode within a couple of months. Which is why, as mentioned earlier, carbides are necessary. DISCUSSION OF ALTERNATIVE MATERIALS Boron carbide is a carbide with a high Vickers hardness value of over 30 GPa, but with relatively lower toughness of around 3 MPa/(m^½). However, research has been performed on remedying this by adding aluminum to the boron carbide, resulting in a material with high hardness and toughness (Shen et al. 2021). Boron carbide is also resistant to corrosion, but it is not mentioned if this material property persists with the addition of aluminum (Boron Carbide n.d.). REFERENCES Advanced Ceramic Materials. (n.d.). Boron Carbide: key properties & applications. https://www.preciseceramic.com/blog/boron-carbide-key-properties-applications.html Arrayago, I., Real, E., & Gardner, L. (2015). Description of stress–strain curves for stainless steel alloys. Materials & Design, 87, 540–552. https://doi.org/10.1016/j.matdes.2015.08.001 Boron carbide | SICT. (n.d.). https://ceramique-technique.com/en/materials/boron-carbide#:~:text=It%20is%20the%20 third%20hardest,and%20excellent%20resistance%20to%20heat. Eric Ness, Ron Zibbell, Abrasion and erosion of hard materials related to wear in the abrasive waterjet, Wear, Volume 196, Issues 1–2, 1996, Pages 120-125, ISSN 0043-1648, https://doi.org/10.1016/0043-1648(95)06886-4. Gök, K., Ada, H. D., Kilicaslan, N., & Gök, A. (2023). A review of CFD modeling of erosion-induced corrosion formation in water jets using FEA. Journal of Mechanical Materials and Mechanics Research, 6(2). https://doi.org/10.30564/jmmmr.v6i2.5607 Hashish, M. (1994). Observations of wear of Abrasive-Waterjet nozzle materials. Journal of Tribology, 116(3), 439–444. https://doi.org/10.1115/1.2928861 H. Syazwani et al 2016 IOP Conf. Ser.: Mater. Sci. Eng. 114 012020 https://iopscience.iop.org/article/10.1088/1757-899X/114/1/012020/pdf Schlick, J. (2023, July 24). What is a water jet nozzle: Definition, types, materials & specifications. TechniWaterjet. https://www.techniwaterjet.com/waterjet-nozzle/ Shen, Y., Fuller, J., & An, Q. (2021). Mitigating the formation of amorphous shear band in boron carbide. Journal of Applied Physics, 129(14). https://doi.org/10.1063/5.0044526 Ulbrich. (2020, July 1). The basics of stainless steel temper Conditions. Ulbrich. https://www.ulbrich.com/blog/the-basics-of-stainless-steel-temper-conditions/ Water jet cutting (Hydrodynamic cutting). (n.d.). Water Jet Cutting (Hydrodynamic Cutting). https://www.open.edu/openlearn/science-maths-technology/engineering-technology/man upedia/water-jet-cutting-hydrodynamic-cutting#:~:text=The%20jet%20has%20a%20velo city,but%20the%20more%20power%20required What are garnet abrasives. (2022). BARTON. https://www.barton.com/what-are-garnet-abrasives Yidi Shen, Jon Fuller, and Qi An,“Mitigating the formation of amorphous shear band in boron carbide,” Journal of Applied Physics (2021). https://doi.org/10.1063/5.0044526.
