جستجوی مقالات مرتبط با کلیدواژه « Hydrogen Embrittlement » در نشریات گروه « مواد و متالورژی »

In this paper, 50CrV4 steel wire with a diameter of 4 mm were subjected to pure Zn electroplating. The effect of shot peening before and baking after electroplating on tensile performance of steel was investigated. Bombardment was done before plating for 20 minutes with shots 0.5 mm and 58 RC. Baking was performeIn this paper, 50CrV4 steel wire with a diameter of 4 mm were subjected to pure Zn electroplating. The effect of shot peening before and baking after electroplating on tensile performance of steel was investigated. Bombardment was done before plating for 20 minutes with shots 0.5 mm and 58 RC. Baking was performed after plating for 24 hours at 200°C. Finally, the samples were subjected to slow strain rate test, microhardness test and SEM imaging. The results showed that the effect of baking on improving the mechanical life of the sample under tension alone is greater than the shot peening. The mean time to failure of plated and baked samples was 2.5 hours, but for shot and plated samples was 2.1 hours. The simultaneous effect of pre-plating shot peening and post-plating baking led to further improvement of the tensile performance of the wire and the mean failure time reached 3.55 hours in the slow strain rate test. The embrittlement susceptibility index is now reduced from 0.76 for only plated samples to 0.13 for shot peened and baked samples, which shows a very good improvement. The effect of shot peening on the tensile properties of steel can be attributed to the formation of a residual compressive stress layer on the substrate surface, which leads to a reduction in the growth rate of microcracks due to tensile stresses under working conditions. The results also showed that due to the baking, continuous microcracks are created in the coating / substrate interface, which provide suitable paths for hydrogen to leave the substrate. after plating for 24 hours at 200°C. Finally, the samples were subjected to slow strain rate test, microhardness test and SEM imaging. The results showed that the effect of baking on improving the mechanical life of the sample under tension alone is greater than the shot peening. The mean time to failure of plated and baked samples was 2.5 hours, but for shot and plated samples was 2.1 hours. The simultaneous effect of pre-plating shot peening and post-plating baking led to further improvement of the tensile performance of the wire and the mean failure time reached 3.55 hours in the slow strain rate test. The embrittlement susceptibility index is now reduced from 0.76 for only plated samples to 0.13 for shot peened and baked samples, which shows a very good improvement. The effect of shot peening on the tensile properties of steel can be attributed to the formation of a residual compressive stress layer on the substrate surface, which leads to a reduction in the growth rate of microcracks due to tensile stresses under working conditions.

The aim of this study is to reach an increased service life for parts using in sour environment by weld overlaying process. In this investigation¡ two successive layers of ER410NiMo were clad on low alloy steel substrates. To reduce the likelihood of Hydrogen Induced Cracking (HIC) and producing stable hydrogen traps¡ Post Weld Heat Treatment (PWHT) was conducted. Microstructural analysis¡ X-ray diffraction studies¡ and mechanical tests show significant increase for austenite volume fraction after second stage of PWHT. In fact¡ not only two-stage PWHT reduce the samples hardness¡ but it also increases austenite volume fraction which is a more resistant microstructure against hydrogen cracking.

In this paper, the hydrogen embrittlement of the high strength Cr-Si spring steel with after Zn-12%Ni electroplating, have been evaluated. Slow strain rate test with 3.34 × 10-6 sec-1 strain rate was performed, and the hydrogen embrittlement index of the different samples was calculated. The effect of baking after plating and also the effect of applying a nickel interlayer by electroless method, is examined by using the weibull statistical model. The results showed that alloying Zn with nickel considerably reduce the diffusion of hydrogen on the substrate steel structure. So that it increases the average failure time of samples from 4.9 hours for pure Zn to 8.7 hours for Zn-Ni. By applying nickel interlayer, the failure time increased to 11.15 hour. Baking after the electroplating of Zn-Ni samples without interlayer, leaded to an increase in the failure time to 10.15 hours. While baking in samples containing nickel interlayer, showed the opposite effect, reducing the failure time to 8.15 hours.

Diffusion of hydrogen in metals and alloys will affect the material behavior such as loss in mechanical properties. In this research the effect of alloying element on the hydrogen diffusion of the cladding AISI 347 with several different chemical compositions has been evaluated. For this purpose a piece of carbon steel St37 was prepared and cladding with filler metal with two different chemical compound 347 stainless steel. In this regard، a non-hazardous electrochemical charging method to hydrogen charge the specimens.. Mechanical properties and microstructure of the specimens were studied by means of micro hardness testing، tensile strength، toughness، optical microscopy and microanalysis techniques (EDS). Results indicate that both overlays were without any defects in the interfaces. Also the results of the cladding samples showed the presence of elements such as Cr، Mn، Ti، Nb can reduce hydrogen permeation and diffusion، while Ni probability can increase permeation and hydrogen embrittlement.

Dissimilar joints between austenitic stainless steels and low alloy and carbon steels have many usages in various industries and also have economic aspects. Loss of mechanical properties can be influenced by existence of hydrogen in corrosive enviroments. The effects of hydrogen on joints between carbon steel (A516) and stainless steel (AISI347) are compared and discussed in this research. For this reason samples made up from low-alloy steel prepared, then cladded with stainless steel 321 and Er347 by process of Gas Tungsten arc welding (GTAW). Then cladded samples putted under hydrogen cathodic charging. Ultrasonic tests, metallography, hardness measurment, bending and microscopic analysis (EDS) have used in order to compare these mechanical properties with uncharged samples. Result of these experiments shows that both materials, showed corrosion resistance against corrosive areas, but samples have broken from their interface while using force and penetrating hydrogen into it. In other hand it was seen separation in the interface of A516-Gr70 and AISI 321. Totally results show that AISI 347 clad shows better resistance than covered C-Steel with AIS 321.