The Influence of Ni on Bainite/Martensite Transformation and Mechanical Properties of Deposited Metals Obtained from Metal-Cored Wire

The multi-pass deposited metals were prepared by metal-cored wire with low (2.5 wt%) and high (4.0 wt%) Ni to research the effect of Ni on the bainite/martensite transformation. Results showed that deposited metals exhibited a multiphase structure comprised of bainite, martensite and residual austenite, which is not only explained from SEM/TEM, but also identified and quantified each phase from crystallographic structure through XRD and EBSD. With Ni content increasing, the fraction of martensite increases from 37% to 41%, and that of bainite decreases from 61% to 55% accordingly because 4% Ni element narrows the temperature range of the bainite transformation ~20 °C. The 7.8% residual austenite exhibited block and sheet in the deposited metal with low Ni, while the fraction of residual austenite was 3.26% as a film with high Ni, caused by different transformation mechanisms of bainite and martensite. The tensile strengths of deposited metals were 1042 ± 10 MPa (2.5% Ni) and 1040 ± 5 MPa (4% Ni), respectively. The yield strength of deposited metals with high Ni was 685 ± 18 MPa, which was higher than low Ni due to the high fraction of martensite. The impact values of deposited metals with high Ni content decreased because the volume fraction of bainite and residual austenite and area fraction of large-angle grain boundary were lower.

Comparison of microstructure and mechanical properties of plastic mould steel for physical application

In this paper, plastic mold steel S136 and S136 SUP were studied for microstructural observation and mechanical properties through metallographic, SEM, EDS, XRD, hardness test and impact test. The results showed that after the same heat treatment, the martensite structure of S136 SUP was denser, the carbides were more uniform and finer, and the hardness was slightly lower but the toughness was greatly increased compared with that of S136. the residual austenite content of S136 and S136 SUP were 2.46% and 10%, respectively, and the heat treatment hardness was 50.1 HRC and 49.1 HRC, respectively. The impact toughness was 90.6 J and 299.1 J.

Possibility of applying X-ray methods to control the surface quality of a shaft line after finishing

The purpose of the paper is to analyze the application limits of X-ray methods of non-destructive testing of loaded parts; to compare the results of microstresses and deformations of the details’ surface layer by methods and by the method of X-ray diffraction analysis for various modes of processing the detail surface layer. The studies are carried out on a “Dron” diffractometer. The technique and algorithm of X-ray structural studies, namely, “sin2v|/”-method are represented. Residual macro σφ and micro stresses, as well as the sizes of the areas of coherent scattering (D) on the samples surfaces processed in various modes, and their distribution in the near-surface layer are designated. Phase analysis is conducted and the presence of residual austenite. The research object is the operating surface of the 46-19-186 gear tooth after various treatments: after HFC hardening; after HFC hardening, grinding and blasting in depressions; after HFC hardening and fine-finish cutting. The X-ray structural analysis (XRD) technique is presented to determine the residual macro-σφ and microstresses, the sizes of the coherent scattering regions (D) on the surfaces of the samples processed in different modes. The outcomes of X-ray structural analysis are compared with the outcomes of metallographic studiesmaking. It was determined that the stress relaxation during the manufacture of the sample is no more than 10%, and the total instrumental error of the X-ray spectral analysis method is about 1%.

Influence of 3d-printing parameters on the mechanical properties of 17-4PH stainless steel produced through Selective Laser Melting

Additive Manufacturing (AM) is a technological process in which elements are fruitfully built up adding materials layer by layer. AM had a massive development in recent times, thanks to its intrinsic advantages, especially if compared with conventional processes (i.e. subtractive manufacturing methods), in terms of free-form design, high customization of products, a significant reduction in raw materials consumption, low request of postprocessing and heat treatments, use of pure materials and reduced time for final products to be marketed. In order to give an innovative contribution to the knowledge in the field of metal AM materials, this paper reports the main outcomes of an experimental campaign focused on the influence of several specific printing parameters on the mechanical features of the 17-4PH stainless steel, which is one of the most used metal for the Selective Laser Melting (SLM) technology. The influence of different printing directions and sample inclinations on the material mechanical behavior is assessed, with the aim of considering an innovative use in the field of structural engineering. Moreover, the effects due to scanning and recoating times are studied. In addition, the consequences of heat treatment (annealing) on both the residual stresses and the amount of residual austenite are appraised.

Fine structure of low-carbon steel after electrolytic plasma treatment

This work shows the results of research of the fine and dislocation structure of the transition layer of 18CrNi3Mo low-carbon steel after the influence of electrolytic plasma. Conducted research has shown that the modified steel layer, as a result of carbonitriding, was multiphase. Quantitative estimates were made for carbonitride М23(С,N)6 in various morphological components of α-martensite and on average by material in the transition layer of nitro-cemented steel. It was established that α-phase is tempered martensite after nitrocementation. Released martensite is represented by batch, or lath and lamellar low-temperature and high-temperature martensite. Inside the tempered martensitic crystals, lamellar cementite precipitates are simultaneously present, and residual austenite is found along the boundaries of the martensitic rails and plates of low-temperature martensite. It was determined that inside the crystals of all morphological components of α-martensite there are particles of carbonitride М23(С,N)6.

Preparation and wear properties of high-vanadium alloy composite layer

A high-vanadium alloy composite layer was prepared on the surface of a carbon steel using cast composite technology, and the wear properties of the composite layer were investigated. The results showed that the microstructure of the composite layer was composed of primary vanadium carbides (VC), flake martensite, residual austenite, and fine VC. The hardness of the cast alloy layer was 63 HRC. The abrasive wear resistance and impact wear resistance were increased by 60% and 26%, respectively, compared with those of high-chromium cast iron. The excellent wear resistance of the cast alloy layer is attributed to the high-hardness primary vanadium carbide and the large number of fine secondary vanadium carbides precipitated out of the cast alloy layer.

Analysis of the influence of hot rolled plate steel treatment using temper and quench-temper method on vickers hardness number enhancement

This paper wants to know the effect of bending radius on the distribution of hardness, grain distribution and microstructure on the surface area of tensile stress and compressive stress after bending, quenching and tempering. Material testing helps determine and analyze material quality. The research was conducted on the bending of Hot Rolled Plate Steel material with a radius of 50 mm, 55 mm, 60 mm, 65 mm and 70 mm with a measurement distance of 1 mm, 2 mm and 3 mm, the highest value was obtained at a radius of 55 mm with a measurement distance of 1 mm. After getting the quench-temper treatment with a holding time of 30 minutes, the value of 498 HV was obtained at a radius of 70 mm with a measurement distance of 2 mm. Hardness test was performed using the austenite temperature of 900 °С, microstructure test results obtained finer grains in the compression area r=2.173 µm and in the tensile area r=2.34 µm. This observation aims to determine the microstructure of the material undergoing a heat treatment process at a temperature of 900 °С with a holding time of 30 minutes using water cooling media. The results of the observation of the microstructure of the test specimens before the quench-temper process showed that the structure of ferrite was more abundant than perlite, but after the quench-tempering process the results showed that there was more perlite than ferrite due to the presence of austenite. The treatment on the transformation of the Ar3 line causes the hardness to change the shape of the martensite microstructure into steel while the thickness of the carburizing layer increases with the increase in the carbonization temperature on the surface of the quenched specimen, resulting in the formation of martensite and residual austenite causing the coating to become hard.

Characteristics of Impulse Carburization LPC Process

In the present work, Pyrowear53 steel was subjected to the impulse carburizing LPC process. After carburation, the material was quenched and tempered. Postprocessing analyses included the measurement of hardness, carbon content, residual austenite, and residual stresses. The results revealed that the thermochemical treatment resulted in the formation of an approximately 1200 µm wide carburized layer. The results of hardness, carbon content, and residual austenite measurement showed a continuous gradient (drop) in the measured values within the carburized layer. However, the results of residual stresses revealed the existence of a local extremum, namely, a zone with higher compressive stresses at the depth between 600 and 1000 µm. This was explained by a different temperature for initiation of martensite transformation as a function of carbon content. This difference resulted in the occurrence of two martensite expansion fronts at two different depths, resulting in an increase in compressive stresses at the noted depth range. Moreover, it was concluded that this region was present for material containing between 0.8 and 0.4 wt% carbon for Pyrowear53.