The changes occurring in the microstructure and mechanical properties of interrupted G115 steel samples during creep at 650 °C and 140 MPa were systematically investigated. M23C6 carbides exhibited a low coarsening rate in the G115 steel upon the addition of boron. Cu-rich phase particles can significantly stabilize the microstructure in the early stages of creep. However, they gradually dissolved after ~ 1000 h. The geometrically necessary dislocation (GND) density decreased significantly during the transient creep stage and was relatively stable after 1045 h. Finally, it decreased rapidly. The mean width of the martensite lath structures increased slightly with an increase in the creep time from 0 h to 302 h, after which it dramatically increased, which is closely related to the evolution of Cu-rich phase particles. On the basis of the obtained experimental results, a microstructural-based yield strength model was developed for establishing the correlation between the microstructure and mechanical properties of G115 steel at different creep stages. The results calculated by the model were in good agreement with the experimental data.

A physical-based yield strength model for the microstructural degradation of G115 steel during long-term creep

Nitriding can improve the surface hardness and wear resistance of metals, and rare earths can speed up this process. To study the mechanism of rare earths promoting salt bath nitriding, GX-8 steel ...

Acceleration effects of rare earths on salt bath nitriding: diffusion kinetics and first-principles calculations

Bearing is a mechanical element that resembles a loaded shaft, so that rotation or back and forth motion can be smooth, safe and long lasting. Bearings should be sturdy and durable to allow the shaft and other machine elements to work properly. If the bearing is not working properly then the performance of the whole system will decline or not work properly. For this reason, materials from high-carbon steel bearings should be durable and durable. To obtain the desired properties of the metal, the Heat Treatment process, especially the outer and inner ring, is used. Hardness testing of the outer and inner ring of the bearing is performed after the Heat Treatment process. Testing the violence using the Digital Rockwell Hardness Tester, the value of the violence can be read directly on the scale of the tool. The Heat Treatment process of the outer and inner ring of the bearing can produce the mechanical properties that the manufacturer wants, namely Rockwell hardness 62-64 HRC. If the result of the hardness test is in accordance with the factory standard, then the outer and inner ring meet the manufacturer's quality requirements.

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Hardness Analysis of Bearing on Heat Treatment Process

Size effects of Y-enriched intermetallic precipitates in Fe-20Cr-5Al-0.25Y alloy on the spallation resistance of thermally grown α-Al2O3 scales

Size Effects on Dissolution Kinetics of Y-Enriched Precipitates in FeCrAlY Alloys During High-Temperature Oxidation

First-Principles Study of Phase Stability and Solubility in Fe-RE (Y, La, Ce) Alloys

The effects of antimony (Sb) on the deformation behaviour of high-grade non-oriented silicon steel at a low temperature were studied by using a Gleeble-3800 thermal simulator and the field-emission scanning-electron microscope. The tensile strength of the high-grade non-oriented silicon steel without Sb was significantly lower than that of the high-grade non-oriented silicon steel with Sb within the tensile temperature range of 25 °C–240 °C. It is possible for Sb atoms near the grain boundary to diffuse at hundreds of atoms through dislocations as a rapid diffusion channel, which is driven by thermal activation with an increase in temperature. Atomic diffusion can weaken the damage to bonding forces on the grain boundary and crack propagation along the grain boundary under load action. The segregation of Sb atoms at the grain boundary decreased gradually, which weakened the cleavage characteristics of the fracture morphology and enhanced its dimple characteristics. For a stretching temperature of 80 °C, the fracture dimple of high-grade non-oriented silicon steel without Sb was significantly more than the high-grade non-oriented silicon steel with Sb. Because of the weakening effect of Sb segregation at the grain boundary, the suitable low-temperature deformation range for high-grade non-oriented silicon steel with Sb was 120 °C–160 °C.

Effect of antimony on low-temperature tensile deformation behaviour of high-grade non-oriented silicon steel

Age-hardening behaviour of steel bearing 155-Cu was studied at different holding timeMicrohardness testing during aging treatment in high purity steel bearing copper was carried outBy means of ZEISS metallographic microscope,X-ray diffractometer and JEM-2010 HREM,the microstructure of high purity steel bearing copper during isothermal aging treatment was observedThe corresponding relationships between isothermal aging process and microhardness,microstructure were analyzed in this paperThe result showed that when aging temperature was increased,the holding time arriving at aging peak was shorter and the aging peak hardness was lowerAt over-aging process of 550 ℃ aging treatment,there were a large numbers of Cu-rich clusters distributed in the ferrite matrix,the size of which was about 20～72 nmWith the holding time,the rich-copper particles were coarsened,and thus led to microhardness decreasing

Ageing Behaviour of Fe-1.55Cu Alloy

The heat treatment of quenching,tempering and isothermal quenching process was used on GCr18Mo steel.Meanwhile,the microscopic structure and the hardness value of GCr18Mo steels were analyzed and compared under different heat treatment processes.It is found that the hardness value of GCr18Mo steels quenched at 930 ℃ and tempered at 180 ℃ is lower than GCr18Mo steels quenched at 860 ℃and tempered at 220 ℃.The microscopic structures in both heat treatment proesses are tempering martensite+carbide+residual austenite.Volume fraction of lower bainite increase gradually with the extension of isothermal time,whose structure pattern changes from acerose to hassock stack.The hardness value of GCr18Mo steels austenitized at 930 ℃ and isothermally quenched at 230 ℃ for 130 minutes are lower than GCr18Mo steels austenitized at 870 ℃ and isothermally quenched at 230 ℃ for 30 minutes.

Effect of heat treatment processes on microstructure and hardness of GCr18Mo steel

Effect of solution and aging process on microstructure and hardness of Fe-1.12%Cu steel was investigated.The precipitation process was observed by optical metallography and JEOL JEM-2010 electron microscope (TEM). The results show that there are lots of uneven ordering domain after solution treatment. Transition phases (B2) form continuously in ordering domain from aging initial stage to peak appearance which is as result of the structure strengthening of combination of precipitation phases (B2) and ordering domain.

Wang Hai-yan

Papers

First-Principles Study of Phase Stability and Solubility in Fe-RE (Y, La, Ce) Alloys

Effect of antimony on low-temperature tensile deformation behaviour of high-grade non-oriented silicon steel

Ageing Behaviour of Fe-1.55Cu Alloy

Effect of heat treatment processes on microstructure and hardness of GCr18Mo steel

Solution and Aging Process of High Purity Steel Containing Copper