Surface Hardening
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2021 ◽  
Vol 3 (3) ◽  
pp. 91-95
Author(s):  
Zahraa Noori Yassen ◽  
Israa Mohammed Hummudi

Background: Phosphate-bonded investments produce a refractory cast model with rough surface and undesirable properties. Dental Surface hardening agents are then applied to refractory investment materials to enhance its properties. Purpose: compare and evaluate the effects of different dental cast hardening agents (Bees wax, Carnauba wax, and Ceresin wax) on surface roughness of refractory model investment material.  Approach: 30 specimens were constructed from commercially available phosphate bonded investment material. Specimens were subjected to a roughness test before dipping in handing agents, then divided into three groups according to the type of wax in which they were dipped. (10 specimens for each type). Surface roughness test was done by a profilometer where three readings were taken for all the specimens' surfaces randomly. The mean was then extracted for the roughness values before and after dipping in waxes.                                                                                                                                                 Results: the mean and standard deviation were tabulated and statistically analyzed using students T- test. The roughness values were decreased after the specimens were dipped in waxes (P value < 0.001 HS highly significant). Conclusion: The dipping process with hardening agents has significantly improved the surface roughness of the specimens' investment materials.


2021 ◽  
Vol 19 (1) ◽  
pp. 48-59
Author(s):  
T. G. Bunkova

The article presents surface hardening technology as applied to solid-rolled wheels of rolling stock. The obtained results of the theoretical study on the process of strengthening the metal of the wheel will make it possible to develop scientifically grounded technological and technical solutions to prevent formation and development of defects on the rolling surface, as well as to eliminate them during maintenance.The objective of this work is to identify the optimal method for surface hardening of a railway wheel with defects.At present, the issue of extending service life of elements and critical parts of rolling stock is becoming increasingly acute. Due to the limited economic feasibility and limited availability of existing production technologies, it becomes necessary to create a new material modified with nanoclusters and hardened with surfactants.Nanoclusters have high plasticity and hardness values. To determine the hardness value of nanomaterials, the Vickers hardness test method is used, in which hardness is determined by the size of the area of the indentation after removing the load from the pyramid shaped diamond.Superplasticity is observed in nanostructures. For nickel and nickel-aluminium alloy NiAl3, low-temperature superplasticity is observed in the temperature range 450–470°C, which is three times lower than their melting point.


2021 ◽  
Vol 3 (2) ◽  
pp. 109-114
Author(s):  
Melya Dyanasari Sebayang

A surface hardening process by adding carbon to its surface without changing the core properties of the material is called the carburization process. This process is carried out at the austenite temperature so that the carbon can diffuse into the phase. This process can only be done on low carbon steels with a content of below 0.25%. This research uses ST 37 steel which is a low content steel with a carbon content of 0.18%. This type of steel is surface hardened with a carburizing temperature of 850°C for a long lasting time of 1 hour, then it is carried out under moderate cooling with outside air media. This research produces a carburizing method with carbon battery media that easily breaks down into steel, which occurs in carbon batteries at temperatures below 723°C. And change its mechanical properties from the comparison of the initial mechanical properties of the specimen. Carburizing with battery rock media is more efficient at temperatures below 723°C. Because of at temperatures below austenite or below the carburizing temperature of carbon from the batteries, it can absorb the surface of the steel even though the amount is still very small. Because the temperature is below the austenite temperature, the absorbed carbons cannot diffuse as happened in the carburization process, but the absorbed carbons can bind the grain boundaries so that they change their hardness by 4%. The microstructure in the research that occurs in this process has nothing to change its phase because the temperature does not reach the austenite temperature.


2021 ◽  
Vol 9 (10) ◽  
pp. 437-444
Author(s):  
Shuyuan Gou ◽  
Shunchao Li ◽  
Hailei Hu ◽  
Youtong Fang ◽  
Jiabin Liu ◽  
...  

Coatings ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 997
Author(s):  
Huizhen Wang ◽  
Yuewen Zhai ◽  
Leyu Zhou ◽  
Zibo Zhang

Laser surface hardening is a promising surface technology to enhance the properties of surfaces. This technology was used on the 42CrMo press brake die. Its hardening behavior was investigated by using scanning electron microscopy and electron backscattering diffraction. The results indicated that the martensite in the hardening zone was significantly finer than that in the substrate. There were many low-angle grain boundaries in the martensite of the hardening zone, and the kernel average misorientation and grain orientation spread in the hardening zone grains were obviously greater, which further improved the hardness of the hardening zone, especially near the substrate. The microstructure and the properties of the blade maintained excellent uniformity with treatment by single-pass laser surface hardening with a spot size of 2 mm, scanning speed of 1800 mm/min, and power of 2200 W. The hardness of the hardening zone was 1.6 times higher than that of the base material, and the thickness of the hardening zone reached 1.05 mm.


2021 ◽  
Vol 410 ◽  
pp. 463-468
Author(s):  
Alexander V. Shaparev

Contact surfaces preparation before cold cladding is one of the most important technological operations. A joint plastic components deformation of the of bimetal 1 according to OST 3-6648-91 and bimetal 3 according to OST 3-6649-91 CuZn10 brass - C22E steel - CuZn10 brass (according to EN standard) should be performed with the strongest possible compression to obtain the required layers connection strength, ensuring strip winding into a roll without delamination. We investigated influence of some factors on the bond strength of bimetal layers: surface hardening of contact surfaces, presence of an underlayer on a steel base, contact surfaces micro geometry, components heating temperature in the deformation zone, diffusion annealing after cladding and a bimetal layers thicknesses ratio effect. Cold cladding technological recommendations have been developed for manufacturing of bimetal 1 according to OST 3-6648-91 and bimetal 3 according to OST 3-6649-91 (CuZn10 brass - C22E steel - CuZn10 brass).


Materials ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4358
Author(s):  
Jörg Weise ◽  
Dirk Lehmhus ◽  
Jaqueline Sandfuchs ◽  
Matthias Steinbacher ◽  
Rainer Fechte-Heinen ◽  
...  

Metal foam inserts are known for their high potential for weight and vibration reduction in composite gear wheels. However, most metal foams do not meet the strength requirements mandatory for the transfer of sufficiently high levels of torque by the gears. Syntactic iron and steel foams offer higher strength levels than conventional two-phase metal foams, thus making them optimum candidates for such inserts. The present study investigates to what extent surface hardening treatments commonly applied to gear wheels can improve the mechanical properties of iron-based syntactic foams. Experiments performed thus focus on case hardening treatments based on carburizing and carbonitriding, with subsequent quenching and tempering to achieve surface hardening effects. Production of samples relied on the powder metallurgical metal injection molding (MIM) process. Syntactic iron foams containing 10 wt.% of S60HS hollow glass microspheres were compared to reference materials without such filler. Following heat treatments, the samples’ microstructure was evaluated metallographically; mechanical properties were determined via hardness measurements on reference samples and 4-point bending tests, on both reference and syntactic foam materials. The data obtained show that case hardening can indeed improve the mechanical performance of syntactic iron foams by inducing the formation of a hardened surface layer. Moreover, the investigation indicates that the respective thermo-chemical treatments can be applied to composite gear wheels in exactly the same way as to monolithic ones. In the surface region modified by the treatment, martensitic microstructures were observed, and as consequence, the bending limits of syntactic foam samples were increased by a factor of three.


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