Joining of microwave sintered Fe-26Al, Fe-30Al, Fe-26Al-14Ti and fe30al-14Ti powder mixtures by diffusion bonding using cu interlayer

Bu çalışmada, mikrodalga sinterleme yöntemi ile 550 ○C de 1 saat süreyle sinterlenmiş Fe-26Al, Fe-30Al, Fe-26Al-14Ti ve Fe-30Al-14Ti toz karışımlarının, elektrolitik bakır aratabaka kullanılarak difüzyon kaynağı yöntemiyle birleştirilebilirliği araştırılmıştır. Sinterleme sonrası Fe-30Al ve Fe-30Al-14Ti karışımlarında B2(FeAl) düzen kristal yapısının oluştuğu ancak Fe ve Al alaşımlarında ortaya çıkan diğer bir düzen kristal yapısı olan D03(Fe3Al) kristal yapının oluşmadığı gözlemlenmiştir. Difüzyon kaynağı, 550 ○C de 1 saat bekleme süresi ile gerçekleştirilmiş ve kaynak bölgesine uygulanan kesme dayanım testleri sonucunda, Cu aratabakalı difüzyon kaynağı ile birleştirilen numunelerin kesme mukavemetlerinin bileşimden bağımsız olduğu bulunmuştur. Ortalama kesme dayanım değerleri 23 MPa olarak ölçülmüştür. Karışımı oluşturan Fe, Al ve Ti tozlarının kendi arasında ve bu tozların temas halinde olduğu Cu aratabaka ile yayınım reaksiyonuna girdiği, SEM çalışması sonucunda görülmüştür. Bu bölgelerde element dağılım analizi yapılarak kimyasal reaksiyonlar ve difüzyon kinetiği hakkında bilgi elde edilmiştir.In this study, the joinability by diffusion bonding of Fe26Al, Fe26Al14Ti, Fe30Al and Fe30Al14Ti elemental powder mixtures microwave sintered at 550○ C for 1 hr have been investigated by using electrolytic Cu interlayer. Following the sintering, the ordered B2(FeAl) phase was observed in the specimens Fe30Al and Fe30Al14Ti, however, another type of ordered phase of D03(Fe3Al) which is found in Fe-Al alloys was not detected in any of the powder mixtures examined in this study. Diffusion bonding was carried out at 550○ C for 1 hr and it was shown that, based on the results from shear testing applied on the weld zone of diffusion bonded specimens, shear stresses of the specimens diffusion bonded by using Cu interlayer are independent of composition. The average shear stress was measured to be 23 MPa. Scanning electron microscopy (SEM) studies revealed that a diffusion zone was observed within elemental powders of Fe, Al and Ti that form the mixtures and in Cu interlayer that is in contact with these elements. Elemental distribution analysis on these zones was also made in order to predict the chemical reactions and their kinetics in the diffusion bonded area

Performance of resistance spot weld caps coated with Ni and Fe aluminide alloys by electro spark deposition on hot dip galvanized steel

Resistance spot welding (RSW) is widely used as a main joining technique in industry and the electrode caps are frequently replaced because of the degradation during service. In this study, the G type copper RSW electrode caps were coated with Fe and Ni based Fe3Al, FeAl, Ni3Al, NiAl alloys by Electro-Spark Deposition (ESD), providing resistance to hot deformation, oxidation and Zn evaporation from sheet metal. The ESD coated electrode caps were tested in-situ on a hot dip galvanized steel in order to assess the performance of RSW electrode caps. For this purpose, three different coating voltages were selected for each coated electrode, and 12 different cap coatings were produced in total. Fifty resistance spot welds were consecutively manufactured with the same parameters for each type of coating electrodes. Hardness measurements, macrostructural examination, Ultrasonic Testing (UT) and chisel tests were performed on welded samples produced. In addition, effects of different coatings on RSW electrode caps were investigated on microstructural development, hardness variations and deformation capacity of resistance spot welds. Results showed that chisel tests and cross section thickness values of the welded sample made with the caps that were ESD coated with the Ni3Al electrode produced better results than the other caps. The cross-sectional thickness of nuggets was lower in all 158 V coated caps. The performance of aluminide coatings on RSW electrode caps can be listed from the best to the worst in the order of Ni3Al, NiAl, Fe3Al, and FeAl

Diffusion bonding of electroless Ni plated WC composite to Cu and AISI 316 stainless steel

In this study, a composite containing WC (Tungsten Carbide) and Ni was produced by two different processing routes. Electroless Ni coated WC powders were consolidated and sintered at 1200 ◦C. Diffusion bonding couples of WC(Ni)-electrolytic Cu, WC(Ni)-AISI 316 stainless steel and WC(Ni)-WC(Ni) were manufactured by using a preloaded compression system under Ar atmosphere. Diffusion bonding was carried out at varying bonding temperatures; 750 ◦C for (WC)Ni-Cu diffusion couple and 1200 ◦C for (WC)Ni-(WC)Ni and (WC)Ni-AISI 316 stainless steel diffusion couples. Standard metallographic techniques, Scanning Electron Microscopy, and a shear test was employed to characterize the microstructure of bonding and mechanical properties of each diffusion couple, respectively

The effect of voltage on the arc stud welding of microwave sintered Fe+Al powder mixture

The joining of powder metallurgy products is of importance because of high demand in many industrial applications. In this study, the effect of welding voltage on the joint quality has been investigated using discharge arc stud welding, a low heat input welding method, without gas protection to join steel stubs to microwave sintered compacts containing a powder mixture of 26 atomic % Al and Fe (balance). It has been shown that welds with steel stubs are prone to side cracking in the weld zone and they also suffer from the oxidation of metal powders adjacent to the weld zone. The forms of oxides are continuous and laminar type in welds with steel stubs and the composition of weld zone changes with increasing arc voltage

Electrochemical corrosion behavior of high velocity Oxy-Fuel (HVOF) superalloy coatings on ductile irons

In this study, alloyed and unalloyed ductile irons (DI) were coated with two different Ni-based superalloy materials by HVOF method. Microstructure and phase analyzes of the coatings were performed by using SEM, EDX, XRD methods. The electrochemical corrosion behavior of alloyed and unalloyed DI is investigated in 3.5% (w / v) NaCl solution. As a result of the characterization studies, it was observed that a dense non-porous coating layer of about 80 μm thickness was obtained on the cast iron samples and continuous adhesion was provided between the coating and the substrate. It has been determined that the cast iron coated with AMDRY 9624 contains γ matrix and β intermetallic phases and the coating produced with AMDRY 9951 commercial powder contains only γ phase. As a result of coating process, the corrosion rate of the alloyed and unalloyed spherical graphite cast irons is reduced. Also, the corrosion rate of the coating produced with AMDRY 9951 is higher than the coating produced with AMDRY 9624

Ni-al-ti kompozit üretimi ve mekaniksel özelliklerinin incelenmesi

Intermetallic materials such as NiAl are among advanced technology materials that have outstanding mechanical and physical properties for high temperature applications. Especially creep resistance, low density and high hardness properties stand out in such intermetallics. It is known that Ni-Al intermetallics are commonly used in various application fields with the addition of Ti, in particular as well as elements such as Co, Cr, Mo and Fe which are related to this group for improving properties thereof. It is especially determined that Ti additive provides positive results in terms of low density, high hardness and shear strength in the produced intermetallics. Given this information, sintering process was used in this study by adding different amounts of Ti powder to Ni-Al powder mixture. When the properties of the sample after sintering were examined we were able to reveal the effects of Ti on Ni-Al and consider 4% Ti added composition as the most suitable ratio in terms of mechanical properties. Analyses were conducted metallographically on the samples after sintering, the densities were calculated and hardness and shear strengths were determined. According to the data while 4% Ti added composition had 5.1 gr/cm3 of density and 186.4 HB hardness values, 2% Ti added composition displayed 224 MPa shear strength.NiAl gibi intermetalik malzemeler, yüksek sıcaklık uygulamaları için olağanüstü mekanik ve fiziksel özelliklere sahip ileri teknoloji malzemeleri arasındadır. Özellikle sürünme direnci, düşük yoğunluk ve yüksek sertlik özellikleri bu tür metallerde göze çarpmaktadır. Ni-Al intermetalliklerinin yaygın olarak Ti ilavesiyle birlikte çeşitli uygulama alanlarında, özellikle de bunların iyileştirilmesi için bu gruba bağlı Co, Cr, Mo ve Fe gibi elementlerin kullanıldığı bilinmektedir. Özellikle Ti katkı maddesinin üretilen intermetaliklerde düşük yoğunluk, yüksek sertlik ve kayma dayanımı açısından olumlu sonuçlar verdiği tespit edilmiştir. Bu bilgiler ışığında, Ni-Al toz karışımına farklı miktarlarda Ti tozu eklenerek sinterleme işlemi yapılmıştır. Sinterleme sonrası numunenin özellikleri incelendiğinde Ti'nin Ni-Al üzerindeki etkilerini ortaya çıkarılmış ve mekanik özellikler açısından en uygun oran olarak % 4 Ti katkılı kompozisyonu olarak görülmüştür. Sinterlemeden sonra numuneler üzerinde metalografik olarak analizler yapılmış, yoğunluklar hesaplanmış, sertlik ve kayma dayanımları belirlenmiştir. Verilere göre % 4'lük Ti katkılı bileşim 5,1 gr / cm3 yoğunluğa ve 186,4 HB sertlik değerine sahip olduğu görülmüştür

Changes in mechanical and morphological properties of AISI 420 stainless steels welded with M42 steel wire Associated with weld cooling medium

Bu çalışmada, AISI 420 martenzitik paslanmaz çeliklere TIG kaynak yöntemiyle Argon gazı korumalı ortamda, 75 amper 45cm/dk kaynak ilerleme hızıyla kaynak dikişleri çekilmiştir. Bu amaç için Ø 50mm çapında ve 2, 3.5, 5 ve 6.5 mm kalınlıklarında disk şeklinde parçalar hazırlanmıştır. 50 mm boyunca kaynak dikişi oluşturulan bu parçaların kaynaktan hemen sonra farklı soğutma sıvılarına daldırılarak oda sıcaklığına kadar soğumaları sağlanmıştır. Deney numunelerinin sertlik ölçümü kaynak dikişinden esas metale doğru gerçekleştirilmiştir. Mikroyapı karakteristikleri ise optik mikroskop, taramalı elektron mikroskobu (SEM) vasıtasıyla incelenmiştir. Sonuç olarak, östenitik yapının yüksek soğuma hızından etkilenerek martenzitik yapıya dönüşmesi gerçekleşmiştir. Bu tür paslanmaz çeliklerin kritik soğuma hızının altında soğutulmaması için uygun tedbirlerin alınması gereklidir.In this study, the method AISI 420 TIG welding of martensitic stainless steels in the protected environment of Ar gas and 75 amps and with a weld speed of 45cm/min was carried out. For this purpose, specimens of Ø 50mm diameter and thickness of 2, 3.5, 5 and 6 mm was sliced. Weld bead was formed along the specimen for about 50mm long and following the welding, specimens were immersed into a different cooling fluids to cool to room temperature. Microhardness measurement was carried out mainly from the base metal towards the weld seam. Microstructural characteristics were investigated by optical microscope, scanning electron microscopy (SEM). As a result, the martensitic transformation of the austenitic structure has been influenced by the high cooling rate. This type of stainless steel must not be cooled below a critical cooling rate and it is necessary to take the appropriate measures

Effects of silicon and chromium additions on glass forming ability and microhardness of Co-based bulk metallic glasses

111-115Effects of<span style="font-size:9.0pt;mso-bidi-font-size:10.0pt;mso-ansi-language: EN-GB" lang="EN-GB"> silicon and chromium<span style="font-size:9.0pt; mso-bidi-font-size:10.0pt" lang="EN-US"> additions on glass forming ability (GFA) and microhardness of a Co-Fe-Ta-B bulk metallic glass are investigated by using differential scanning calorimetry (DSC), X-ray diffractometry (XRD) and scanning electron microscopy (SEM). It is found that partial substitution of boron by silicon promotes the GFA of the alloy. Fully amorphous rod of 4 mm is fabricated by suction casting Co43Fe20Ta5.5B26.5Si5 alloy. However, partial replacement of cobalt by chromium decreased the GFA significantly. In fact, critical casting thickness of Co39Cr4Fe20Ta5.5B26.5Si5 alloy is determined as 2 mm. It is also determined that microhardness values of the amorphous alloys are about 1200HV300. This value is lower than the hardness of the base alloy,1455HV300, and it is believed that decrease in hardness results from the reduction in boron contents of the alloys. </span

Investigation of corrosion and wear behavior of borided AISI P20 steel in micro-wave furnace

In this study, the effect of microwave boronizing treatment on the corrosion and wear behaviour of boride layer formed on AISI P20 steel have been investigated. The boronizing treatment was carried out using Ekabor-II powders at temperatures of 800, 850 and 900 °Cfor 2, 4 and 6 h in a micro-wave furnace. Electron and optical microscopy, x-ray diffraction and hardness measurements were used to characterize the boride layers. The corrosion behaviour was also studied using electrochemical methods in a 1MNaCl solution and the wear behaviour was examined using the ball-on-disk wear method. Studies showed that the boride layer contained the phases of FeB, Fe2B, CrB andMnBand boride layer thickness was affected by the increase in boronizing time and temperature. Boronizing treatment contributed positively to the wear resistance by increasing the surface hardness and by decreasing the friction coefficient