eJournals International Colloquium Tribology 23/1

International Colloquium Tribology
ict
expert verlag Tübingen
125
2022
231

Effect of Lubricants on Hydrogen Permeation under Rolling Contact of Steel

125
2022
Yoji Sunagawa
Hiroyoshi Tanaka
Joichi Sugimura
ict2310277
23rd International Colloquium Tribology - January 2022 277 Effect of Lubricants on Hydrogen Permeation under Rolling Contact of Steel Yoji Sunagawa Idemitsu Kosan Co., Ltd., Chiba, Japan Corresponding author: yoji.sunagawa.0470@idemitsu.com Hiroyoshi Tanaka Kyushu University, Fukuoka, Japan Joichi Sugimura Kyushu University, Fukuoka, Japan 1. Introduction In rolling bearings used in automotive electrical instruments, power transmission parts such as CVT (Continuously Variable Transmission) and wind turbines, early bearing failure accompanied by white microstructures below the raceway subsurface occurs. The main cause is often thought to be the effect of hydrogen embrittlement. Hydrogen embrittlement is the process by which steel materials become brittle and fracture due to the introduction and subsequent diffusion of hydrogen into the metal. In rolling bearings, since active nascent metal surface is exposed, lubricant oils between metal surfaces is decomposed, and hydrogen is generated and penetrates into steels. 2. Experimental This study describes the effects of lubricant additives on the generation and permeation of hydrogen into AISI 52100 bearing steel in rolling contact. Lubricated tests were conducted in a nitrogen atmosphere. PAO was used as the base oil. Sample A and sample B were formulated with representative detergent additives. Oil decomposition test (Test 1) and rolling contact fatigue test (Test 2) were conducted. 3. Results In Test 1, the lubricant oil was decomposed by the effect of catalyst (Fe) and the amount of hydrogen generation was measured by gas chromatograph. Sample A showed two times higher hydrogen generation rate than that of the base oil, whereas Sample B reduced the hydrogen generation rate, as shown in Fig. 2. In Test 2, the fatigue life was evaluated using a thrust bearing type rolling test apparatus. Thermal desorption spectrometry (TDS) was used to measure the amount of permeated hydrogen immediately after the rolling test. The test revealed that the fatigue life increased in order of base oil, Oil B, Oil A, as shown in Fig. 4. TDS analysis revealed that the amount of permeated hydrogen was in the order of Oil A, Oil B, base oil. These results suggested that the amount of permeated hydrogen and the fatigue life were inversely correlated. Table 1: Test samples Figure 1: Hydrogen generation test apparatus (Test 1) 278 23rd International Colloquium Tribology - January 2022 Effect of Lubricants on Hydrogen Permeation under Rolling Contact of Steel Figure 2: Hydrogen generation test results The process of hydrogen permeation can be broken down into mainly two phases at nascent metal surface. One is dissociation at C-H bond in oil skeleton. The other is diffusion of hydrogen atoms on the metal surface. In the second phase, a part of atomic and/ or ionic hydrogen recombine to produce gaseous hydrogen. The others may permeate into the steel. The balance of the two processes may cause hydrogen content in the steel under rolling contact. The detail which effect of the two detergent additives on the hydrogen permeation process will be discussed. Figure 3: Fatigue life test apparatus (Test 2) Figure 4: Fatigue life test results References [1] Sadeghi, F., Jalalahmadi, B., Slack, T.S. Raje, N., and Arakere, N.K., “A Review of Rolling Contact Fatigue”, J. Tribol., 131, 4, 2009, 041403-1. [2] Tanaka, H., Niste, V.B., Abe, Y., and Sugimura, J., “The effect of lubricant additives on hydrogen permeation under rolling contact”, Tribol. Lett., 65, 3, 2017, 94.