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• Failure analysis of refrigerator compressor crankshaft was studied. • Serious abrasive wear has occurred on the surface of the crankshaft. • The failure of the crankshaft is caused by the cutting of particles inside the compressor on the surface of the friction pair. • Nano copper layer was prepared by in-situ gas nitriding process, which provided a new modification technology for precision friction pair. With the improvement of family life quality and the implementation of energy-saving green household appliances, the volume of refrigerator increases rapidly and the energy efficiency ratio continues to decrease. However, the compressor size is required to be smaller, and the startup and shutdown are more frequent, which aggravates the wear of crankshaft connecting rod. Here, the failure compressor (300 ppm) provided by the manufacturer was disassembled and analyzed. The results showed that there were abrasive wear and adhesive wear on the surface of crankshaft and connecting rod. The source of solid particles in compressor was further analyzed, and the process control measures were proposed. In addition, combined with its failure mechanism and production process, the crankshaft surface composite treatment process was designed and bench test was carried out, which shows excellent anti-wear and self-lubricating performance. [ABSTRACT FROM AUTHOR]

Metal surface nanocrystallization can improve the surface activity, reduce the diffusion activation energy, and then reduce the diffusion temperature or time. However, for gradient nanostructured surface layer on 32Cr2Mo1VE prepared by surface ultrasonic rolling process (SURP), the surface nanocrystallization seriously hindered the diffusion of N atoms during gas nitriding (430 °C, 480 °C and 530 °C). The effect of the distribution of alloying elements on the diffusion of active N atoms was studied in detail. For multi-element medium‑carbon alloy steels, it should be that carbides or nitrides formed by alloying elements usually precipitate easily at grain boundaries. So, precipitates along grain boundaries will block the rapid diffusion channel of nanocrystalline grain boundaries and also reduces the concentration gradient drive. • After surface ultrasonic rolling process (SURP), the surface grains were refined. • After SURP, the carbides were refined and precipitated on the grain boundaries. • The Cr 2 N precipitated on the grain boundaries of the SURP sample after gas nitriding. • The carbides and Cr 2 N formed on the grain boundaries hinder the diffusion of N atoms. [ABSTRACT FROM AUTHOR]

[Display omitted] • CrN ultrafiltration membranes with 121 L/m2·h·bar were successfully prepared. • Preparation process by in-situ gas-solid catalytic reaction at 800 °C. • TiO 2 additive play an important role in gas-solid reaction of Cr 2 O 3 nanoparticles. • The molecular weight cut off (MWCO) of CrN membranes was around 1740 Da. To expand the industrial application of membranes, high-performance CrN tight ultrafiltration membranes (UF) were prepared by in situ gas–solid reaction using Cr 2 O 3 as a nanoprecursor and TiO 2 as a nitriding catalyst in ammonia atmosphere. The phase composition and microstructure of CrN UF membranes were characterized by X-ray diffraction and field-emission scanning electron microscopy with energy-dispersive X-ray spectroscopy. The effects of TiO 2 and sintering parameters on the crystalline phase and pore size of CrN UF membranes were investigated. The results identified Ti4+ as a key factor influencing the transformation of the Cr 2 O 3 phase into the CrN phase. The as-prepared CrN membranes exhibited enhanced hydrophilicity, no cracks or pinholes, water flux of 121 L·m−2h−1 bar−1, and a molecular weight cut-off of 1500 Da. The membranes also had retention rates of 100% for methyl blue (50 ppm) and 90% for methylene blue (50 ppm), which almost remained constant under repeated use. [ABSTRACT FROM AUTHOR]