Cr3C2 incorporation into an Inconel 625 laser cladded coating: Effects on matrix microstructure,mechanical properties and local scratch resistance

There is an increasing industrial demand for metal alloys with high wear resistance under severe operating conditions. Ni-based alloys, such as Inconel superalloys, are an excellent option for these applications; however, their use is limited by their high cost. Ni-based coatings deposited onto carbon steel substrates are being developed to achieve desired surface properties with reduced cost. Laser cladding deposition has emerged as an excellent method for processing Ni based coatings. In this work, microstructure, mechanical properties and local wear behaviour have been investigated in response to the addition of Cr₃C₂ ceramic particles into an Inconel 625 alloy deposited onto a ferritic steel substrate by laser cladding. Using this deposition technique, a homogeneous distribution of Cr₃C₂ particles was observed in the coating microstructure. The addition of ceramic particles to the starting powder resulted in the formation of hard precipitates in the coating microstructure. The partial dissolution of Cr₃C₂ particles during the laser cladding process increased the hardness of the Inconel 625 matrix. Depth sensing indentation and scratch tests were performed to study the local wear behaviour and scratch resistance of the cermet matrix compared with the conventional Inconel 625 alloy. Finally, the effect of Cr₃C₂ on mechanical properties was correlated with the observed microstructure modifications.     

不同填充材料下316LN/Inconel 718异种激光焊接头的显微组织与力学性能

目的研究不同填充材料下316LN/Inconel 718异种激光焊接接头的显微组织、显微硬度及室温拉伸性能。方法分别对316LN/Inconel 718异种材料在不填充焊丝、填充ER316LMn焊丝和填充HGH4169焊丝的情况下进行激光对接试验。采用XJP-2C型倒置光学显微镜观察不同填充材料下接头的显微组织,401MVD型数显显微硬度计测量不同填充材料下接头显微硬度,WDW-100型万能电子试验机测量不同填充材料下接头的室温拉伸抗拉强度,最终,对不同填充材料下316LN/Inconel718激光焊接接头的显微组织和力学性能进行对比分析。结果不填充焊丝与填充ER316LMn焊丝时,可获得外观成形良好的焊接接头;填充HGH4169焊丝时,接头外观成形稍差,但力学性能较好;不填充焊丝时,焊缝组织主要为柱状树枝晶、胞状晶和等轴树枝晶,填充焊丝时,焊缝组织主要为柱状树枝晶和胞状晶。填充焊丝和不填充焊丝情况下,316LN侧熔合区均会产生分层现象,而Inconel 718侧熔合区分层现象则不明显;当填充HGH4169焊丝时,焊缝的显微硬度值与抗拉强度值最大,焊缝填充ER316LMn焊丝时次之,不填充焊丝时最小。接头抗拉强度最大值为764.59 MPa,接头断裂方式为典型的韧性断裂。结论填充焊丝较不填充焊丝时,接头的力学性能有所提高,且填充HGH4169焊丝时,接头的力学性能达到最佳,但焊缝的宏观成形难以控制。     

Effect of pre- and post-weld heat treatment on metallurgical and tensile properties of Inconel 718 alloy butt joints welded using 4 kW Nd:YAG laser

The effects of pre- and post-weld heat treatments on the butt joint quality of 3.18-mm thick Inconel 718 alloy were studied using a 4 kW continuous wave Nd:YAG laser system and 0.89-mm filler wire with the composition of the parent metal. Two pre-weld conditions, i.e., solution treated, or solution treated and aged, were investigated. The welds were then characterized in the as-welded condition and after two post-weld heat treatments: (i) aged, or (ii) solution treated and aged. The welding quality was evaluated in terms of joint geometries, defects, microstructure, hardness, and tensile properties. HAZ liquation cracking is frequently observed in the laser welded Inconel 718 alloy. Inconel 718 alloy can be welded in pre-weld solution treated, or solution treated and aged conditions using high power Nd:YAG laser. Post-weld aging treatment is enough to strengthen the welds and thus post-weld solution treatment is not necessary for strength recovery.     

热处理工艺对Inconel718合金组织、力学性能及耐蚀性能的影响

对高含H2S/CO2酸性油气田封隔器材料-Inconel718镍基合金进行固溶处理和时效处理,研究不同热处理工艺条件下合金的组织、力学性能、耐蚀性能之间的关系。结果表明:随着固溶温度的升高,δ相不断溶入基体。材料经时效处理后析出第二相γ″相,硬度和强度明显高于固溶处理的样品,1000℃固溶+720℃×8h→50℃/h620℃×8h时效处理的样品硬度和强度达到最大值。高温高压H2S/CO2介质中挂片实验的结果表明,不同热处理的Inconel718合金均具有良好的耐腐蚀性能,经固溶处理的材料耐腐蚀性略优于经固溶+时效处理的材料。高温高压H2S/CO2应力腐蚀实验的结果表明,Inconel718没有发生应力腐蚀开裂迹象。综合考虑耐蚀性能和力学性能,确定Inconel718合金的最佳热处理工艺为:1000℃固溶1h+720℃×8h→50℃/h620℃×8h时效。     

RF／DC溅射316L／SiO2复合膜力学性能与显微结构的研究

利用射频／直流磁控测射法制备了316L不锈钢／SiO2复合薄膜,并对其组织,相结构和力学性能进行了测试分析,结果表明,直流磁控溅射316L不锈钢薄膜呈柱状晶结构,主要由Fe-Cr和r-Fe相构成,在Fe-Cr(110)晶面出现明显择优取向,由于SiO2的掺合,使316L不锈钢／SiO2复合薄膜柱状晶变细小,出现明显的二次柱状晶,Fe-Cr的（110）晶面掺优取向消失,而Fe-Cr的（211）晶面衍射峰强度明显增强,316不锈钢膜硬度明显高于316L块体,掺入SiO2的金属／陶瓷复合薄膜耐磨性有显著的提高。     

Effect of TiC Content on Mechanical Properties and Microstructure Evolution of TiC/Inconel 718 Functionally Gradient Materials by Direct Energy Deposition

TiC/Inconel 718 functionally gradient materials are prepared by direct energy deposition technology. The effect of TiC content on microstructure and mechanical properties of TiC/Inconel 718 functionally gradient materials is studied. With the increase of TiC content, the microhardness and carbide grain of the specimen are improved, and the density is reduced. The grain of the specimen changes from columnar dendrites to equiaxed crystal, and the equiaxed crystal size is decreased with the increase of TiC content. However, when TiC content is above 10 wt%, the number and size of the Laves phase, coarse TiC primary, and TiC secondary dendrite are increased which causes the generation of cracks. When the TiC content is above 5 wt%, the size of carbide and the number of cracked UMT increase and the impact toughness decreases. Therefore, the optimal maximum TiC content of TiC/Inconel 718 functionally gradient materials is 5 wt% when the laser power is 2200 W.     

Structure and wear resistance of the composite layers produced by glow discharge nitriding and PLD method on AISI 316L austenitic stainless steel

The rapid technical development enhances the demands on constructional materials in terms of their resistance to frictional wear, resistance to corrosion and erosion, high hardness, high tensile and fatigue strength. These demands can be satisfied by e.g. applying various surface engineering techniques that permit to modify the microstructure, phase and chemical composition of the surface layers of the treated parts. A prospective line of the development of surface engineering is the production of composite layers by combining various surface engineering methods. The paper presents the results of examinations of the phase composition and frictional wear resistance of the layers produced by hybrid processes, i.e. such that combined glow discharge assisted nitriding performed at 450 °C and 550 °C with a pulsed laser deposition of boron nitride coatings (PLD method). It has been shown that the boron nitride coatings formed on nitrided AISI 316L steel increase its frictional wear resistance.     

Structure and wear resistance of the composite layers produced by glow discharge nitriding and PLD method on AISI 316L austenitic stainless steel

The rapid technical development enhances the demands on constructional materials in terms of their resistance to frictional wear, resistance to corrosion and erosion, high hardness, high tensile and fatigue strength. These demands can be satisfied by e.g. applying various surface engineering techniques that permit to modify the microstructure, phase and chemical composition of the surface layers of the treated parts. A prospective line of the development of surface engineering is the production of composite layers by combining various surface engineering methods. The paper presents the results of examinations of the phase composition and frictional wear resistance of the layers produced by hybrid processes, i.e. such that combined glow discharge assisted nitriding performed at 450 °C and 550 °C with a pulsed laser deposition of boron nitride coatings (PLD method). It has been shown that the boron nitride coatings formed on nitrided AISI 316L steel increase its frictional wear resistance.     

Multisheet structure of Inconel 718 superalloy processed by LBW/SPF technology and its microstructure

Abstract

Multisheet structure of Inconel 718 superalloy will be widely used in vehicles as heat resisting and heat shielding structure due to its lightweight, high strength and stiffness. Multisheet structure of Inconel 718 superalloy was processed by laser beam welding and superplastic forming (LBW/SPF) technology in the present paper. Multisheet structure of Inconel718 superalloy processed by LBW/SPF technology exhibits good configuration and uniform thickness distribution. Laser beam welding parameters for multisheet structure were as follows: pulse frequency was 32 Hz; pulse duration 3 ms; peak power per pulse 4500 W; welding speed 180 mm min^–1; SPF parameters were as follows: temperature T_f=965°C; forming pressure P _f=4·2 MPa; forming time t _f=130 min. Microstructure of multisheet structure was studied carefully. Microstructure in weld fusion zone was constituted of austenite dendritics and Laves phase precipitated in interdendritics. After SPF process, austenite dendritics in the weld fusion became coarser and most of Laves phases were dissolved and turned into δ precipitated phase but a few of Laves phases were still reserved. And Nb concentration in dendritics increased to 5·42% compared to 2·82% under as welded condition. Weld metal hardness increased from 331·63 under as welded condition to 391·74 under post-SPF condition which was closed to the base material hardness of post-SPF. Grain size of base material grew slightly and an amount of precipitated phase appeared in the base material undergoing SPF process. The tensile test results of base material show that tensile strength increased obviously and the ductility decreased slightly after SPF process. Therefore, LBW/SPF technology is an appropriate forming technique for multisheet structure of Inconel 718 superalloy.     

Tribology of laser modified surface of stainless steel in physiological solution

The laser surface treatment of stainless steel (SS) 316L, an important alloy for biomedical applications, was used to improve its corrosion and wear-corrosion resistance in bio-environment. Microstructural and X-ray diffraction (XRD) pattern analysis showed presence of an austenitic phase in both untreated and laser-treated SS316L. Laser melting produced homogenized and refined microstructure on the surface with higher hardness (143–171 HV) compared to untreated SS316L (131 HV). Increase in intensity of γ (200) peaks in XRD pattern for laser-treated (>800 W) SS316L indicated possible crystallographic orientation along γ (200) plane. Passive currents were reduced to <2.8 μA/cm² and pitting potentials was increased to >+344 mV for samples laser surface treated at greater than 1200 W. The volume-loss and wear-rate of laser-treated SS316L were significantly reduced compared to untreated sample. Abrasive wear was the main wear mechanism for both untreated and laser surface treated SS316L. Wear particles/debris were found to be cold welded on the surface of SS316L and showed brittle cracking with further wear-straining.     

Laser Processing of Advanced Bioceramics

In this article, laser processing of diamondlike carbon‐metal nanocomposite films, hydroxyapatite‐osteoblast composites, and Ormocer® microdevices for medical applications is described. Pulsed laser deposition has been used to process diamondlike carbon‐silver‐platinum nanocomposite films that provide hardness, wear resistance, corrosion resistance, and antimicrobial functionalities to cardiovascular, orthopaedic, biosensor, and MEMS devices. Laser direct writing has been used for fabricating integrated cell‐scaffold structures. Two photon induced polymerization has been used to create Ormocer® tissue engineering scaffolds and microneedles with unique geometries. Pulsed laser deposition, laser direct write, and two photon induced polymerization techniques may provide medical engineers with advanced biomaterials that possess unique structures and functionalities.     

Cover Picture: Laser Processing of Advanced Bioceramics (Adv. Eng. Mater. 12/2005)

In this article, laser processing of diamondlike carbon‐metal nanocomposite films, hydroxyapatite‐osteoblast composites, and Ormocer® microdevices for medical applications is described. Pulsed laser deposition has been used to process diamondlike carbon‐silver‐platinum nanocomposite films that provide hardness, wear resistance, corrosion resistance, and antimicrobial functionalities to cardiovascular, orthopaedic, biosensor, and MEMS devices. Laser direct writing has been used for fabricating integrated cell‐scaffold structures. Two photon induced polymerization has been used to create Ormocer® tissue engineering scaffolds and microneedles with unique geometries. Pulsed laser deposition, laser direct write, and two photon induced polymerization techniques may provide medical engineers with advanced biomaterials that possess unique structures and functionalities.     

Dual Coating Laser Cladding of NiCrBSi and Inconel 718

This paper presents an alternative approach to obtaining crack- and pore-free NiCrBSiFeCuMoC hard coatings on a low alloy steel substrate through coaxial laser cladding, by using Inconel 718 as a buffer layer between the hard coating and the base material. The presence of the buffer layer reduces the overall cracking susceptibility of the hardfacing material by reducing the compressive stresses developed during the cladding process and ensuring a more uniform heat distribution gradient at the surface of the material than the base metal alone, which provides an additional hardness and wear coefficient increase of 7% and improves the corrosion resistance of the obtained materials by 20%, in comparison with the reference sample obtained without an intermediate layer, by using the same operational parameters and minimizes elemental dilution with the substrate. Our method could prove useful in increasing the quality and life cycle of expensive high-performance hard-coated materials, especially those working under demanding operational and environmental conditions.     

激光快速成形316L不锈钢研究

介绍激光快速成形316L不锈钢的有关情况，研究了不同激光和扫描速度情况下，单道激光熔覆层及多道搭接的组织及宏观形貌，研究了不同工艺条件下所制备薄壁墙的组织及性能，在此基础上进行了简单外形块体材料及复杂外形薄壁零件的制备。研究表明，采用激光快速成形制备的316L不锈钢零件组织致度，成分均匀，具有快速凝固组织特征，力学性能与铸造及锻造退火态相当，可满足直接使用要求。     

Powder bed binder jet 3D printing of Inconel 718: Densification,microstructural evolution and challenges☆

Traditional manufacturing of Inconel 718 components from castings and thermomechanical processing routes involve extensive post processing and machining to attain the desired geometry. Additive manufacturing (AM) technologies including direct energy deposition (DED), selective laser melting (SLM), electron beam melting (EBM) and binder jet 3D printing (BJ3DP) can minimize scrap generation and reduce lead times. While there is extensive literature on the use of melting and solidification based AM technologies, there has been limited research on the use of binder jet 3D printing. In this paper, a brief review on binder jet additive manufacturing of Inconel 718 is presented. In addition, existing knowledge on sintering of Inconel 718 has been extended to binder jet 3D printing. We found that supersolidus liquid phase sintering (SLPS) is necessary to achieve full densification of Inconel 718. SLPS is sensitive to the feedstock chemistry that has a strong influence on the liquid volume fraction at the processing temperature. Based on these results, we discuss an empirical framework to determine the role of powder particle size and liquid volume fraction on sintering kinetics. The role of powder packing factor and binder saturation on microstructural evolution is discussed. The current challenges in the use of BJ3DP for fabrication of Inconel 718, as well as, extension to other metal systems, are presented.     

Characteristics of Laser-Fabricated Metal Structures

Laser-aided direct fabrication technology is developed to produce three-dimensional metal alloy structures directly from the constituent elements. The shapes of the structures are designed using Computer Aided Design (CAD) tools and are fabricated as real parts by fusing powders with a laser beam. In this study, alloy structures of simple plate like geometry were produced by mixing stainless steel (SS 316) powder with either copper or aluminum powder. The thickness of the component is related to the process parameters through an energy balance equation, which is verified against experimental data. Material properties such as hardness, strength and conductivity are analyzed and optical micrographs are presented to exhibit the microstructure of the alloy. The results show improved hardness at certain locations in the alloy, higher thermal conductivity of stainless steel. However, the structures broke due to brittle failure under tensile loads.     

Machining Characteristics of Inconel 718 by Sinking-EDM and Wire-EDM

Inconel 718 superalloy has wide applications in several industries due to its excellent mechanical properties. However, it is very difficult to machine using conventional cutting and grinding because of its high strength at elevated temperatures. Electrical discharge machining (EDM) is an alternative competitive process to machine Inconel alloys by electrical erosion. However, machinability and surface characteristics of EDMed Inconel surfaces are poorly understood. This study focuses on the machining characteristics of Inconel 718 by Wire-EDM and Sinking-EDM with a new Cu-SiC electrode, respectively. Material removal efficiency, surface roughness, surface topography, surface alloying, and electrode wear have been characterized. It is found that the high toughness of Inconel 718 would be the major contributing factor to the absence of microcracks on the EDMed surface. The new fabricated Cu-SiC electrode for Sinking-EDM has better performance in terms of material removal rate (MRR), surface roughness, and electrode wear. The higher melting temperature and fine microstructure of SiC contribute to the lower electrode wear of the new Cu-SiC electrode than the traditional Cu electrode.     

Residual stresses in laser direct metal deposited Waspaloy

This paper reports a study into the effect of laser pulse length and duty cycle on the residual stress distributions in multi-track laser direct metal deposits of Waspaloy onto an Inconel 718 substrate. The residual stresses have been evaluated using neutron diffraction and the contour method, while electron microscopy and micro hardness indentation have been used to map the concomitant microstructural variation. In all cases, near the tops of the deposited walls, the longitudinal stresses are tensile towards the mid-length of the wall, while the stresses perpendicular to the substrate are negligible. By contrast near the base of the walls, the stresses along the direction of deposition are small, while the stresses perpendicular to the substrate are compressive at the centre and tensile towards the ends. Consistent with previous observations, the stresses parallel to free surfaces are tensile, balanced by compressive stresses in the interior (an inverse quench stress profile). These profiles have been found to be weakly dependent on the laser pulse parameters, most notably an increase in tensile stress gradient with increasing duty cycle, but the maximum residual stresses are largely unaffected. Furthermore, microstructural analysis has shown that the effect of laser pulse parameters on grain morphology in multi-track thick walls is less marked than previously reported for single-track wall structures.     

Laser-treated austenitic steel and nickel alloy for human implants

The recent research in biocompatible materials has been useful in replacing and supporting the fractured natural human bones/joints. Under some condition, negative reaction like release of ions from the bare metal toward the human body fluid leads to corrosion. In this proposed research paper, the biocompatibility of the laser surface-modified austenitic stainless steel (SS316L) and nickel-based superalloy (Inconel 718) was studied. The investigation on laser-modified surfaces is evaluated through electrochemical polarization analysis using simulated body fluid (SBF). The samples subjected to electrochemical polarization analysis were characterized by optical image analysis, SEM, EDS, and XRD analysis. It was inferred that laser surface-modified materials provided enhanced corrosion resistance and bare nickel alloy is more susceptible to corrosion by SBF.     

表面纳米化预处理对316L不锈钢渗氮层摩擦学性能的影响

为改善奥氏体不锈钢的表面硬度和耐磨性,采用超声滚压与离子渗氮复合工艺对316L不锈钢表面进行了表面强化处理。利用扫描电镜(SEM)、硬度计、X射线衍射仪(XRD)和能谱仪以及摩擦磨损试验机等测定了渗氮层的硬度、深度、含氮量和物相组成,研究了表面晶层组织结构对离子渗氮行为和渗氮层在润滑油条件下摩擦学性能的影响。结果表明:直接渗氮和超声滚压/渗氮试样表层组织均由S、γ'、ε和Cr N相组成,渗氮层厚度均为20μm,直接渗氮层以S相为主,超声滚压后渗氮层以ε和γ'相为主,组织结构较为致密;超声滚压/渗氮层的平均渗氮含量是直接渗氮层的2.88倍,摩擦系数降低了0.04,显微硬度和耐磨性是直接渗氮层的1.15倍和2.76倍;超声滚压处理诱使316L不锈钢表面形成的纳米晶层组织结构增强了渗氮试样表面的催渗效能和对渗氮层的支撑强度,超声滚压后渗氮试样的表面耐磨性能最好。