A Test Rig for WSpQ

Release Time：28 Apr,2026

<p style="text-align: center;"><img src="/ueditor/php/upload/image/20260428/1777382625115041.png" title="1777382625115041.png" alt="1.png"/></p><p><span style="font-size: 14px;">A test rig for WSpQ was designed and built. It can be found in Figure 1. The treated components are first austenitized in a vacuum furnace (SyncroTherm). This furnace can be used for neutral hardening (Ref. 3) as well as for low-pressure carburizing (Ref. 4) of single trays of parts (Ref. 5). This is referred to as single-layer vacuum heat treatment. However, for the development of the WSpQ-process, the parts are not quenched in the vacuum furnace, but the hot parts are manually transferred to the WSpQ-test rig.</span></p><p><span style="font-size: 14px;">The test rig for WSpQ consists of two nozzle fields, which are positioned above and below the parts to be quenched, see Figure 2. The nozzle fields—consisting of nine nozzles each—can be independently adjusted in terms of: distance between nozzles and parts to be quenched, flow rate of water, flow rate of compressed air.</span></p><p><span style="font-size: 14px;">In the test rig, water is circulated in a closed loop. No losses due to steam formation or similar effects were observed. The tray size of this test rig is one-quarter that of the SyncroTherm furnace. The decision was made not to construct the test rig at full scale to reduce the initial financial investment for the development works. Results A series of tests was performed on several specimen and gear components made from various steel grades. Hardness Figure 3 shows the hardness uniformity of a bolt made of 18CrNiMo7-6 (d = 50 mm, l = 100 mm, m = 1.5 kg) after WSpQ, measured across its cross-section along two measurement lines positioned at a 90-degree angle to each other.</span></p><p><span style="font-size: 14px;">The WSpQ-process provided a complete through-hardening of the bolt. Three different gear-components were quenched using WSpQ. A small gear made of 20MnCr5, a final drive ring gear made of 20MnCr5 and an internal ring gear made of 18CrNiMo7-6 were treated. Figure 4 shows the achieved core hardness values, demonstrating the very high quench intensity of the process.</span></p><p><span style="font-size: 14px;">Cooling Speed Two bolts with diameters of 25 mm and 40 mm were equipped with thermocouples positioned at depths of 3 mm, 7 mm, and 12 mm to measure cooling curves during the quenching process. A portable data logging system was used to measure the cooling curves. The bolts were quenched from 930°C, applying WSpQ. Within just 28 seconds, the bolt with d = 25 mm is fully cooled down to below 100°C, which demonstrates again the very high quenching intensity of the process.</span></p><p><span style="font-size: 14px;">urthermore, a numerical model was used to calculate the heat transfer coefficient (HTC) based on the measured cooling curves. For this purpose, the cooling behavior was analyzed in the temperature range between 900°C and 150°C. HTC values of up to 4,000 W/(m?K) were determined for the WSpQ-process, significantly exceeding those of oil quenching (1,500–2,500 W/(m?K)) and helium-gas quenching (1,000–1,500 W/(m?K)). Surface Appearance and Microstructure After treatment with WSpQ, the components exhibited a smooth but slightly grey surface appearance. No intergranular oxidation (IGO) was detected. Furthermore, no scaling, decarburization, or other surface defects could be found. The case hardening depth (CHD) turned out as expected. Figure 6 shows the microstructure of a bolt (D = 25 mm, L = 100 mm) made of 20NiCrMo2 after WSpQ. The surface exhibits a fully martensitic structure (100 percent martensite), while the core microstructure consists of a mixture of ferrite, pearlite, bainite, and martensite.</span></p><p><br/></p>