Cr Steel Research Articles

Friction and wear characteristics of the nanolaminated ternary transition metal boride: Mn2AlB2

Herein, the wear and friction behavior, under unlubricated sliding in ambient air, of the MAB phase Mn2AlB2 is reported. Various sliding pairs (WC, Al2O3, Si3N4, and chromium-bearing steel 100Cr6) were used in a ball-on-disc apparatus at a normal load of 10 N and a sliding velocity of 20 cm/s. Raman spectroscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy were used to identify the wear mechanisms and tribo-oxidation products involved during the dry sliding contacts. Against WC, Al2O3, and Si3N4, the Mn2AlB2 exhibited wear by tribo-oxidation accompanied with delamination and abrasion, which led to high wear rates on the order of ∼10-3 mm3/N · m and coefficients of friction of 0.72–0.87. However, Mn2AlB2/100Cr6 tribopair showed relatively mild wear behavior. The evolution of COF and wear rate for this tribopair, under different loads (5, 10, 15 N) and speeds (5, 25, 50 cm/s), showed the existence of load and speed thresholds (15 N at 25 cm/s and 10 N at 50 cm/s), beyond which an abrupt transition from mild to severe wear of Mn2AlB2 takes place. Below the thresholds, the Mn2AlB2 surfaces remain undamaged with the formation of a protective transfer layer, composed of a mixture of iron and manganese oxides. Above the thresholds, both friction and wear increase, and the Mn2AlB2 wears by microfracture and grain pullout.

A comparison study on the effect of counter ball material on sliding wear response of SLM-printed biomedical 316L steel

Selected Laser Melting fabricated 316L steel was studied to reveal its microstructural features and the wear properties under dry sliding against counter ball made of different materials (low-alloyed steel 100Cr6, high-alloyed steel 440C, and corundum). It was found that SLM 316L steel featured a fine-dendrite structure of a “fish-scale” pattern which ensured higher hardness (by 2 times) and wear performance (by 21–58 %) as compared to hot-rolled analogue. SLM 316L steel had the same volumetric wear when tested against 100Cr6 and 440C balls; when tested against Al2O3 its wear increased by 3 times relatively steel counter-bodies.

Quantitative Analysis of the Microstructure That Have Effects on the Creep Properties of 9Cr Steel

Quantitative Analysis of the Microstructure That Have Effects on the Creep Properties of 9Cr Steel

Evaluation of Effect of Small Sample Scoop on Life of 9Cr Steel Piping

Evaluation of Effect of Small Sample Scoop on Life of 9Cr Steel Piping

Thickness of small sample for creep property evaluation of 9Cr steel base metal of piping on site

Thickness of small sample for creep property evaluation of 9Cr steel base metal of piping on site

Sampling Processing Precision of Small Specimens from 9Cr Steel Boiler Piping

Sampling Processing Precision of Small Specimens from 9Cr Steel Boiler Piping

Development of Remaining Life Assessment Method and Its Application to 9Cr Steel Pipe in Power Plants

Development of Remaining Life Assessment Method and Its Application to 9Cr Steel Pipe in Power Plants

Examination of Thickness of Small Sample from Base Metal of 9Cr Steel Boiler Piping

Examination of Thickness of Small Sample from Base Metal of 9Cr Steel Boiler Piping

Creep Properties of 9Cr Steel Welded Joint in Long-term Region

Creep Properties of 9Cr Steel Welded Joint in Long-term Region

EFFECT OF HUMIDITY ON TRIBOLOGICAL PROPERTIES OF SELECTED FRICTION JUNCTIONS WITH AN EVALUATION OF ACOUSTIC EMISSION

The study aimed to compare the effect of humidity on the operation of tribological systems. The tested friction and wear are external properties; therefore, their values may differ significantly depending on the operating parameters of the friction junction and environmental conditions. Tribological tests were carried out on a TRB3 tribometer in a dry sliding mode at a relative humidity of 50% ± 5% and 90% ± 5% in the ball-on-disc configuration with a load of 15 N. The friction junction consisted of a sample made of 100Cr6 steel, and three counter-samples were made of 100Cr6, SiC, and Al2O3 steel. The geometric structure of the surface was examined with an optical profiler. The tribological test results showed reduced linear wear and friction coefficient at a relative humidity of 90% ± 5% compare to its 50% ± 5%. The paper also presents the results for the sound recorded in the 16-bit linear PCM standard and analysed in a Spectra-Plus program.

CLASSIFICATION AND MODELLING OF SOUND EMISSION SIGNALS IN SELECTED TRIBOSYSTEMS

The paper presents an analysis of the sound level recorded during dry sliding friction conditions. Balls with a diameter of 6 mm placed on pins were made of 100Cr6 steel, silicon carbide (SiC), and corundum (Al2O3), while rotating discs with a height of 6 mm and a diameter of 42 mm were made of 100Cr6 steel. Each pin and disc system was tested for two values of the relative humidity of the air (50 ± 5% and 90 ± 5%). Models of the A-sound level were developed using regression trees and random forest. The paper presents an analysis of the accuracy of the models obtained. Classifications of the six tests performed on the basis of sound level descriptors were also carried out.

Effect of Mo addition on microstructure, mechanical and machinability properties of Cr-PM steels

In this work, it was investigated the effect of molybdenum (Mo) addition on machinability, mechanical properties, and microstructure of Cr steels produced by using powder metallurgy method. Tensile and hardness experiments were applied to define the mechanical properties of the produced Cr-PM steels. The machining experiments have been also performed without coolant on a CNC vertical machining center at three different cutting speeds (150, 210, and 270 m/min), two different feed rates (0.4 and 0.8 mm/tooth), and constant depth of cut (0.5 mm). The machinability of the alloys was evaluated in regard to surface roughness (Ra) and tool wear (Vb). The results indicated that that Cr-PM steel with 5% Mo addition by weight had the highest yield, tensile strength, and hardness, and the best surface quality was obtained in this sample in terms of surface roughness. However, according to Vb measurement results, the cutting performance of the cutting inserts wasnegative affected by MoC(N), CrC(N), and MoCrC(N) precipitates formed in the microstructure of PM steel.

Damage analysis of rotation speed on corrosion film of 3Cr steel in the CO2 environment with silty sand

The 3Cr steel used as the tubing has serious corrosion damage in a flowing CO2 environment with silty sand. Hence, the investigation for the influence of flow velocity on the corrosion behavior of 3Cr steel has an important and practical significance. It could not only unveil the corrosion damage mechanism of the steel under dynamic conditions, but also provide a theoretical basis for the corrosion protection of the tubing. In this paper, the effect of flow velocity on the corrosion film of 3Cr steel in a CO2 environment with silty sand was investigated by adjusting rotation speed. The results revealed that the corrosion resistance of 3Cr steel was first reduced, followed by enhancing and then reduced as the rotation speed increased. There was a critical rotation speed for the transformation of corrosion mechanism of 3Cr steel, i.e., 600 r/min. When the rotation speed was lower than the critical speed, the mass transfer process of corrosive medium dominated the corrosion resistance of 3Cr steel, and silty sand participated in the formation of corrosion film. The increasing rotation speed accelerated the mass transfer process, which first reduced and then improved the corrosion resistance. When the rotation speed was higher than the critical speed, the shear stress of silty sand played a predominant role. At the same time, silty sand impinged on the corrosion film, and then destroyed the stability of the film, leading to a significant decrease of the corrosion resistance. Silty sand changed from participating in the corrosion film to destroying the corrosion film with increasing rotation speed.

Effect of the Thermo-Mechanical Processing on the Impact Toughness of a 12% Cr Martensitic Steel with Co, Cu, W, Mo and Ta Doping

This paper presents the results of an experimental investigation of a 12% Cr steel where a significant increase in Charpy impact toughness and a slight decrease in ductile-brittle transition temperature (DBTT) from 70 °C to 65 °C were obtained through thermo-mechanical processing, including interim hot forging at 1050 °C with long-term annealing at 1000 °C, as compared with conventional heat treatment. At lower temperatures ranging from −20 °C to 25 °C, the value of impact toughness comprised ~40 J cm−2 in the present 12% Cr steel subjected to thermo-mechanical processing. The amount of δ-ferrite decreased to 3.8%, whereas the size of prior austenite grains did not change and comprised about 40–50 μm. The boundaries between δ-ferrite and martensitic laths were decorated by continuous chains of Cr- and W-rich carbides. M23C6 carbides also precipitated along the boundaries of prior austenite grains, packets, blocks and martensitic laths. Thermo-mechanical processing increased the mean size of M23C6 carbides and decreased their number particle densities along the lath boundaries. Moreover, the precipitation of a high number of non-equilibrium V-rich MX particles was induced by hot forging and long-term normalizing at 1000 °C for 24 h.

Microstructure Evolution and Cooling Characteristics at C−Si−Mn−Cr Steel during Different Quenching Processes

The industrial importance of steel is reflected in the wear resistance, which is related to its changes of microstructure and temperature changes during heat treatment. Herein, C−Si−Mn−Cr steels are produced to understand the microstructure evolution and cooling characteristics during quenching in water and air. The samples of several feature points are selected along the radial direction from the treated steel, and the temperature distribution of steel is obtained via numerical simulations. The microstructures at different temperature feature points and the corresponding hardness are studied. The results show that the quenching processes with the water−air alternating cycle regulate the temperature distribution. Martensite and pearlite phases are primarily formed during water and air cooling, respectively. In the water−air alternating cycle quenching process, the microstructure includes bainite, martensite, and retained austenite. The obtained microstructure is more ideal and the value of hardness is 525.2 HV. The maximum hardness value is 695.3 HV for water quenching, while that for air cooling is 248.2 HV. The microstructure evolution of steel at different positions is closely related to the temperature change in varied quenching processes.

Preparation of composite gradient coating on the surface of 20Cr steel by scanning electron beam surface alloying

Scanning electron beam surface alloying can effectively improve the microstructure of the surface layer of the material. Plasma thermal spraying and scanning electron beam technology were used to conduct molten alloy treatment on the surface of 20Cr steel to study the formation mechanism of the gradient structure of the sample surface. The study found that after scanning electron beam surface alloying treatment, the surface coating of the sample is composed of alloying layer and heat-affected zone. The microstructure of the alloying layer is acicular martensite, lath martensite, retained austenite and the second phase of the mesh structure, the crystal grains in this region are equiaxed, columnar and dendritic crystal. The heat-affected zone is composed of a complete phase transformation zone and a partial phase transformation zone, the microstructure of the complete transformation zone is acicular martensite and lath martensite, and the microstructure of the partial transformation zone is acicular martensite and ferrite.

Creep-fatigue interaction and damage behavior in 9-12%Cr steel under stress-controlled cycling at elevated temperature: Effects of holding time and loading rate

Considering that most creep-fatigue tests were conducted under strain-controlled mode in previous works, creep-fatigue behavior of 9–12%Cr steel under stress-controlled cycling at elevated temperature was investigated in this work. Particular attention was paid to the effects of holding time and loading rate on the deformation and damage behavior. Results indicated that a remarkable creep ratcheting is generally observed in the creep-fatigue tests with the stress ratio of −1. Ratcheting strain and creep damage progress faster as the holding time becomes larger or the loading rate becomes smaller, resulting in the decrease of the number of cycles to creep-fatigue failure.

Exploration of the competing failure during the stress rupture process for 9Cr-CrMoV dissimilar welded joint

The competing failure mechanism between the heat affected zone (HAZ) of CrMoV steel and weld metal (WM) was found by the stress rupture tests for the 9Cr-CrMoV dissimilar welded joints. The stress rupture occurred in the HAZ of CrMoV steel for the welded joint by the 9Cr steel without element W, yet the failure location shifted to the WM for the welded joint by the 9Cr steel with element W. The precipitates in the WM were mainly the Cr- and Mo-rich M23C6 type carbides. While the W-rich particles were detected in the region of the WM near the fusion line. The partially melted BM2 and its movement into the WM during welding could trigger the formation of the W-rich particles. Thus, the formation of the harder and more brittle W-rich particles in the WM near the fusion line is considered as the crucial factor to result in the failure transition.

Plastic Flow Behavior of an Advanced 9Cr Martensitic Heat‐Resistant Steel at High Temperatures

Advanced 9Cr–1.5Mo–1Co–VNbBN martensitic steel is used for thick castings under ultra‐supercritical conditions. The microstructure, including martensitic laths, dislocations, and precipitations, is observed before and after deformation by transmission electron microscope. Steady‐state flow behavior and deformation mechanisms are investigated by analyzing strain‐rate jump test data at 600–650 °C. Results show that the plastic flow behavior of 9Cr steel is well characterized by a stress power law whose apparent stress exponent n is between 20.5 and 27.0 for the three test temperatures. The apparent activation energy of 621 kJ mol is estimated for the plastic flow of this steel, and the stress exponent and apparent activation energy are particularly high. The analysis incorporates the effect of a threshold stress, which is associated with the pinning effect of particles on dislocations. The truly modified stress exponent n0 is 4.6 at all test temperatures after removing the threshold stress, which is close to that of dislocation‐climb deformation, indicating the deformation of this steel can be described as a lattice diffusion‐controlled dislocation‐climb mechanism. Transmission electron microscopy observation is conducted to characterize the interaction of dislocation–precipitate to provide structural evidence for specific deformation mechanisms.

In Situ Synthesis of (M:Nb,Ta)C/Ni35 Composite Coating Cladded on 40Cr Steel.

To improve the wear and corrosion resistance of the pump barrel material (40Cr steel), a (M:Nb,Ta)C/Ni35 composite cladding coating by in situ synthesis of composite carbides was conducted. The effects of ceramic micro-particles content on the phase composition, microstructure of the coating, structural characteristics of (M:Nb,Ta)C and the tribology and electrochemical corrosion behavior were systematically studied. The increase of ceramic micro-particles changed the morphology of (M:Nb,Ta)C with the size from sub-micron to micron. The (M:Nb,Ta)C dispersed along the grain boundary inhibits the growth of the grains. During friction, the spherical structure exhibited a rolling lubrication effect and the petal structure provided a stronger attachment ability to resist the shear. The corrosion occurred at the grains, exhibiting corrosion pits, in which the high content ceramic micro-particles were relatively shallow. Moreover, a few dot corrosion pits were distributed along the grain boundaries without (M:Nb,Ta)C. Therefore, to improve the corrosion resistance, a thin composite carbide coating with good wear and corrosion resistance was prepared.