Effect of WC-10Co on cavitation erosion behaviors of AlCoCrFeNi coatings prepared by HVOF spraying

The (AlCoCrFeNi)_1-X(WC-10Co)_X composite coatings were fabricated by HVOF spraying and their microstructures, mechanical properties and cavitation erosion behaviors were tested. The effects of WC-10Co on the cavitation erosion mechanisms were discussed by compared the differences of volume losses and eroded surface morphologies between the coatings. The cavitation erosion resistance of the coatings was about 3 times as that of the 06Cr13Ni5Mo steel. With the addition of WC-10Co, the cavitation erosion resistance of the coating was slightly increased. In the initial stage of cavitation erosion test, the cavitation erosion damage was concentrated on the interface, which was caused by the uncoordinated deformation and poor mechanical properties of the interface between HEA and WC-10Co. When the WC-10Co distributed below the HEA region, the WC-10Co played a strong supporting role and improved the impact resistance of the HEA region. The cavitation erosion mechanism of the HEA1 coating was lamellar spalling. The cavitation erosion mechanisms of the HEA2 and HEA3 coatings were particles spalling and lamellar spalling.     

Sand erosion and crack propagation mechanism of Cr/CrN/Cr/CrAlN multilayer coating

Herein, we have deposited Cr/CrN/Cr/CrAlN multilayer coatings with various modulation ratios on TC11 alloy substrate using cathodic arc system. The influence of various modulation ratios on microstructure and Al₂O₃ sand erosion behavior of coatings is systematically studied. Results reveal that the coatings are about 200 nm per cycle and total thickness is 8 μm. Five groups of coatings exhibit high hardness (>3000 HV_0.025). The coating with modulation ratio of 12 adhesion can reaches 55 N. The residual stress increases with the decrease of the modulation ratio, but the increase is generally low (less than ?2 GPa). In addition, according to sand erosion test, it is found that sand erosion resistance of multilayer coating is significantly around 5 times higher than TC11 alloy matrix. The erosion morphology shows that a large number of irregular cracks and layered spalling appear on the surface of the coating, indicating that the cracks are constantly initiated under the continuous impact of the sand and gravel，and finally gather together and then spalling. Moreover, dynamic response and stress field of the coating under the impact of single sand (Al₂O₃) are studied by numerical simulations. It is determined that coating cracking is caused by high tensile stress under CrAlN layer. In addition, according to crack propagation morphology and influence of different interfaces between multilayered structures on crack tips, propagation/termination mechanism of cracks is analyzed in detail. Cracks are easy to initiate in hard CrAlN layer and consume a lot of energy after propagating into soft Cr layer, thereby ending at next soft and hard interfaces. These results provide experimental and theoretical support for the study of high tenacity and anti-erosion coating.     

Grain Growth in Ti(C,N)‐Based Cermets During Liquid‐Phase Sintering

Growth behavior of Ti‐based carbonitride ceramic grains in two high‐Mo Ti(C,N)‐based cermets with Ni and Ni–20Cr (wt%) binders was investigated during liquid‐phase sintering under vacuum at 1410°C, using DSC, XRD, SEM, AEM, and EDS. Grain growth occurred primarily through two‐dimensional nucleation and lateral growth. Most significantly, the grain growth kinetics followed the cubic law, which was controlled by the diffusion of dissolved mass through liquid Ni‐based binder phase. However, when Ni–20Cr (wt%) was used as metallic binder, the inner rim of ceramic grains with the typical core‐rim structure was seldom complete, and there were often some fine Ni‐rich and Mo‐rich speckles in their core. In Ni‐rich and Mo‐rich speckles, there were two kinds of microstructure: one consisted of Ni‐based superlattice phase, and the other consisted of Ti‐based carbonitride ceramic phase and unknown phases. The three‐dimensional thermodynamic equilibrium shape of Ti‐based carbonitride ceramic grains evolved from a {111}‐faceted and round ‐edged octahedron to a {111}‐faceted and sharp‐edged octahedron. In addition, the grain growth rate increased, which was mainly attributed to that the decrease of solid/liquid transformation temperature of Ni‐based binder phase led to the increase of the diffusion rate of dissolved mass through liquid Ni‐based binder phase.     

电沉积Ni-P合金镀层耐蚀性的研究

研究了不同磷含量的Ni-P合金镀层在NaCl介质中的耐腐蚀性能。通过浸泡实验,得出不同磷含量的Ni-P合金镀层在w（NaCl）=5%和饱和NaCl溶液中的腐蚀数据,同时还与纯镍镀层、化学镀Ni-P合金镀层、1Cr18Ni9Ti不锈钢以及A3钢进行了比较。     

海绵钛中Fe,Ni和Cr杂质引入过程分析

采用Kroll法,以TiCl4和液态金属镁制备海绵钛,对海绵钛分部位取样,对高Fe, Ni和Cr含量样品进行MLA检测,计算Ti?Mg?Fe, Ti?Mg?Ni和Ti?Mg?Cr三元系的混合焓,研究海绵钛中Fe, Ni和Cr杂质的来源及引入过程。结果表明,海绵钛中Fe, Ni和Cr杂质主要来自钢制(1Cr18Ni9Ti)反应容器,其引入经历了在液态金属镁中溶解和与海绵钛合金化两步。当海绵钛于反应器壁处生成后,其与以单质形式溶于液态金属镁中的Fe, Ni和Cr原子结合将杂质富集。采取反应容器镀膜处理、控制反应区温度、使用低杂质含量的液态金属镁、将海绵钛坨底部与边部分离等措施可有效降低海绵钛中杂质含量。     

防止不锈钢还原气氛高温变色镀层的研制

通过大量试验,研制成功一种新型的镀镍溶液。结果表明,这种新型的镀镍溶液具有优良的电化学性能,极低的镀层内应力,采用这种工艺在不锈钢(1Crl8Ni9Ti)上镀镍可有效地防止其在高温(900℃)氢气气氛下变黑和镀层起泡。实验中比较了两种不同添加剂镀液的电化学性能,包括均镀能力、深镀能力和阴极电流效率等,并测定了镀层的内应力,分析其原因与影响。     

聚氨酯-硬质合金YG8双层涂层的抗磨蚀性能研究

采用聚氨酯喷涂技术和电火花熔覆技术,在基体铸钢0Cr13Ni5Mo表面制备聚氨酯-硬质合金(YG8)双层涂层,表层为聚氨酯涂层,底层为电火花熔覆层YG8;采用扫描电子显微镜(SEM)观察底层熔覆层与基体铸钢结合面的横截面形貌图,发现熔覆层由白亮层、过渡层组成,表面光亮粗糙,与基体冶金结合;并进行磨擦磨损实验和冲蚀实验。结果表明,双层涂层有较小的摩擦系数,抗冲蚀性是基体抗冲蚀性的3.87倍。该双层涂层兼有软、硬涂层的优点,适用于关键零部件的表面防护和二次修复。     

Effect of Binder Content on the Erosive Wear of Ti(C,N)‐Based Cermet in SiO2 Particle‐Containing Simulated Seawater

Erosion of Ti(C,N)‐10 wt% Mo₂C‐15 wt% Ni/Co cermet of different Ni/Co in artificial seawater containing 5 wt% SiO₂ was investigated. Pure Ni‐bonded cermet exhibited the largest wear rate of 35.7*10^?3 mm³/h, which decreased to 17.7*10^?3 mm³/h with the substitution of 30% Ni by Co. Further decrease of Ni/Co ratio resulted in the improvement of erosion resistance. Pure Co binder resulted in the increase hardness from 92.0 to 92.5 HRA and transverse rupture strength from 1510 to 1650 MPa. The erosion resistance was slightly worse due to an increasing hardness and brittleness of the binder phases, but the hard phases still kept the as‐prepared morphology.     

反应器不锈钢搅拌桨的腐蚀与防护

针对反应器1Cr18Ni9Ti不锈钢搅拌浆在使用含氯物料生产中的腐蚀破坏现象，选用4种材料进行现场挂片试验。得出腐蚀是氯离子的点蚀造成的，指出对不锈钢作阳极氧化处理后耐蚀性增强，并建议使用含钼较高的1Cr18Ni9TiMo不锈钢作搅拌浆。     

粘结剂对超音速火焰喷涂碳化钨涂层磨粒磨损性能的影响

采用超音速火焰喷涂(HVOF)工艺在35钢基体上制备了WC-10Ni涂层和WC-12Co涂层,研究了镍、钴这两种粘结剂对WC涂层的显微硬度、摩擦系数和抗磨粒磨损性能的影响,采用扫描电子显微镜观察涂层磨损前后的表面形貌,探讨了WC涂层的磨粒磨损机理。结果表明,以HVOF方法制备的2种WC涂层均有较高的显微硬度,WC-10Ni涂层和WC-12Co涂层与SiC砂纸摩擦副之间的干摩擦系数相差不大。2种涂层在低载荷下均有较好的抗磨粒磨损性能,但在较高载荷下WC-12Co涂层的抗磨性明显优于WC-10Ni涂层。2种涂层的磨粒磨损形式主要为均匀磨耗磨损,磨损机理以微切削和微剥落为主。WC-12Co涂层的磨损表面损伤较轻微,综合性能优于WC-10Ni涂层。     

含氯介质超临界水氧化过程中几种镍基合金腐蚀的实验研究

超临界水氧化过程中,含氯化合物水溶液对普通不锈钢具有极强的腐蚀性. 使用超临界水氧化反应装置,研究了4种镍基合金不锈钢试样(1Cr18Ni9Ti, 316L, 0Cr18Ni12Ti和QLC12)在超临界水氧化过程中(400~620℃, 28~32 MPa)处理含氯废水时的腐蚀情况. 经过30 d的实验,用金相光学显微镜和扫描电子显微镜观测试样腐蚀的形貌. 结果表明,4种合金在15%(w)含氯水溶液中经过超临界水氧化反应均存在腐蚀. 对腐蚀速率进行了测试,其中1Cr18Ni9Ti和316L腐蚀速率较大,而QLC12腐蚀速率最小,为0.06 mm/a, 可用于制造反应器. 实验发现0Cr18Ni12Ti存在晶间腐蚀现象. 同时对腐蚀机理进行了分析.     

0Cr18Mo2与1Cr18Ni9Ti异种不锈钢焊接区显微组织的分析

采用光学显微镜、扫描电镜 (SEM)等设备对 0Cr18Mo2和 1Cr18Ni9Ti异种不锈钢焊接区进行了研究。结果显示该异种不锈钢焊缝及A一侧组织为少量的铁素体和奥氏体 ,但铁素体一侧靠近熔合区附近的铁素体晶粒有长大的倾向 ,这是使热影响区韧性下降的主要因素     

Microstructure and mechanical properties of Ti–C–TiN-reinforced Ni204-based laser-cladding composite coating

In situ Ti(C, N), ring phase, and multi-phase enhanced Ni204-based alloy coating were prepared by adding various Ti/C/TiN ratios particles. The effects of the reinforcement phase on the microstructure, microhardness, tribological property, and microstructure characteristics at the interface between the coating and substrate were investigated. The results show that the coatings with a 5:1 mass fraction ratio of TiN/C exhibits the highest microhardness, which is 3.78 times higher than that of the original Ni204 coating. While, the coating with 21:7:2 mass fraction ratio of TiN/Ti/C exhibits the lowest friction coefficient, which is 4.44 times smaller than that of the original Ni204 coating. The addition of Ti and C particles promotes the precipitation of ring phase and carbides, reduces ceramic agglomeration, alleviates the floating of ceramic particles, and improves the bonding strength of reinforcement phases. Owing to the good mutual solubility among Fe, Ni, and, Cr elements, the diffusion happened at the interface between the coating and substrate.     

Influence of Ni and ZrO2 contents on sintering and mechanical properties of WC-2wt.%ZrO2-1wt.%Ni composites

WC-2wt.%ZrO₂-1wt.%Ni composites were prepared by vacuum pressureless sintering (VPS) and post-hot isostatic pressing (post-HIP). The microstructure, phase composition, densification, hardness, fracture toughness, and flexural strength of composites with different Ni and ZrO₂ contents were systematically investigated. The results show that WC-Ni and WC-ZrO₂-Ni composites prepared by VPS can be densified by the addition of a small amount of Ni as the binder phase. Moreover, the densities of the composites can be further enhanced i.e. the composites are rendered nearly fully dense following HIP while the grains remain fine without obvious growth. The binder Ni and ZrO₂ phases are uniformly distributed in the WC matrix and exhibit high bonding strength with it. The hardness, fracture toughness, and flexural strength of the WC-ZrO₂-Ni composites following HIP could reach 22.4?GPa, 12.0?MPa?m^1/2, and 1101.2?MPa, respectively. Based on the influence of the Ni and ZrO₂ contents on the microstructures and mechanical properties of the WC-2wt.%ZrO₂-1wt.%Ni composites, the fracture mechanism was determined to be governed by the phase transformation of ZrO₂ that led to the development of some micro-cracks followed by deflection, bridging, and branching of the cracks to improve fracture toughness. The composites are mainly composed of elongated triangular prismatic WC grains and ZrO₂ phases, and hence the fracture mode can change such that transgranular fracture becomes the main fracture mode accompanied by a small amount of intergranular fracture. Thus, the flexural strength of the composites can be improved.     

Ti(C,N)-based cermets with fine grains and uniformly dispersed binders: Effect of the Ni–Co based binders

Metallic binder is a key factor affecting the microstructure and mechanical properties of Ti(C,N)-based cermets. To optimize the overall performances, cermets with various weight ratios of Ni/(Co + Ni) ranging from 0 to 1 were fabricated by gas pressure sintering. Microstructure, phase formation, interface structure and related mechanical properties of the sintered cermets were investigated. With the increase of the Ni/(Co + Ni) ratios, the black cores became smaller and grains of Ti(C,N) dispersed uniformly. Compared to the pure Ni or Co, Ni–Co binders accelerated the formation of rim phases, and avoided the nonuniform dispersed binder pools. When the ratio was 0.5, the cermets showed fine grains, uniformly dispersed binders and small lattice misfit of the core-rim interface, exhibiting the optimal mechanical properties, i.e. satisfactory Vickers hardness of 1670 (HV30) Kgf/mm², bending strength of 1970 MPa and Fracture toughness of 8.94 MPa m^0.5. This work sheds light on constructing the relationship between the microstructure, mechanical performance of Ti(C,N)-based cermets and the Ni/Co-based binders.     

Processing and Properties of Ti(C,N)–WC-Based Materials

Two Ti(C,N)–WC powder mixtures, one containing 0.88 wt% Co and the other 6.2 wt% Ni + 2.9 wt% Co, were fabricated by different routes: pressureless and gas-pressure sintering in argon and nitrogen, and hot-pressing under vacuum. The microstructures of all the sintered samples consisted of grains with a core/rim structure, the core being Ti(C,N) and the rim (Ti,W)(C,N). An inner rim also was present at the core/rim interface. The more highly doped materials also had an intergranular Ni-Co-Ti-W binder phase. The compositions and cell parameters of the hard phases, as well as of the binder, were analyzed. The nitrogen partial pressure in the sintering furnace was the main factor that influenced grain growth and phase composition. In fact, sintering under argon enhanced grain growth and was accompanied by a lower tungsten content in the rim. The influence of the microstructure on some mechanical properties (hardness, flexural strength, toughness, and Young's modulus) also was investigated. Flexural-strength values up to 1550 MPa at room temperature and 1200 MPa at 800°C, and fracture-toughness values up to 8 MPa·m^1/2 were measured, depending on the starting composition and processing conditions.     

Effects of Cr3C2 addition on the erosion–corrosion behavior of Ti(C,N)-based cermets

The effect of Cr₃C₂ addition on the erosion–corrosion behavior of Ti(C,N)-based cermets was investigated. The results indicate that the erosion–corrosion resistance of cermets is significantly enhanced by Cr₃C₂ addition due to corrosion resistance and mechanical property improvement. Strengthening of Ni binder phase by Cr atoms dissolution also contributes to the improvement in erosion–corrosion resistance of cermets. With the increase of Cr₃C₂ content, the erosion–corrosion behavior of cermets is classified to corrosion regime, erosion affected corrosion regime, corrosion affected erosion regime and erosion regime. The corrosion resistance of binder plays an important role in the erosion–corrosion degradation of cermets. Erosion damage is covered by severe corrosion of binder phase for the cermets with low Cr₃C₂ addition, while for the cermets containing high Cr₃C₂ content, the material deterioration is governed by the mechanical impingement of solid erodents.     

Spark plasma sintering of WC-based cermets/titanium and vanadium added composites: A comparative study on the microstructure and mechanical properties

In an attempt to develop the composition and properties of W₂C-(W,Ti)C-TiC and WC-WC_1-x-VC-V super hardmetals, spark plasma sintering (SPS) method was implemented. WC powders were mixed separately with 10?wt% Ti and 10?wt% V in a high energy mixer mill and sintering processes were performed at temperatures of 2150 and 2000?°C, respectively. XRD investigations revealed the formations of TiC and (Ti,W)C as the reaction products in WC-10?wt% Ti composite. Moreover, the interfacial reaction between WC and V led to the formation of WC1-x and VC compounds. A higher bending strength (613?±?25?MPa) and fracture toughness (4.1?±?0.58?MPa?m^1/2) were obtained for WC-10?wt% V samples compared to WC-10?wt% Ti, While the WC-10?wt% Ti composite showed a higher value of hardness (3128?±?42 Vickers) in comparison to WC-10?wt% V (2632?±?39 Vickers), which can act as a super hard cermet.     

(Ni-W-P)-SiC复合镀层的脉冲电沉积及其耐蚀性

研究了(Ni—W—P)—SiC复合镀层的脉冲电沉积工艺及耐蚀性。结果表明：(Ni—W—P)—SiC复合镀层的脉冲电沉积速率比直流电沉积大,脉冲镀层的耐蚀性优于直流镀层和1Cr18Ni9Ti不锈钢;脉冲频率和占空比对镀层的沉积速率、镀层成分以及镀层的耐蚀性都有较大的影响。     

渗铝Q235钢的渗层组织和抗高温氧化性能

分析了Q2 3 5钢热浸渗铝和铝硅合金层的显微组织 ,并对其抗高温氧化性能进行了研究。热浸渗层由镀层 (表层 )和化合物层 (内层 )两层组成 ,金相和X射线能谱分析 (EDS)结果表明纯铝渗层的化合物层呈厚齿状 ,由η相 (Fe2 Al5)组成 ;铝硅合金渗层的化合物层呈薄带状 ,由Si合金化的η相即Fe2 (Al Si) 5组成。热浸渗层经扩散退火后 ,表面镀层消失 ,渗层由表及里依次出现 η相、ζ相、β2 相、β1相和固溶体α相等过渡组织。 80 0℃高温氧化试验结果表明 ,渗纯铝Q2 3 5钢的抗高温氧化性能优于 1Cr1 8Ni9Ti不锈钢 ,硅的加入可以改善热浸工艺性能 ,但降低了渗层的抗高温氧化性能。