SiC-MoSi_2/ZrO_2-MoSi_2 coating to protect C/C composites against oxidation

To improve the oxidation resistance of carbon/carbon （C/C） composites in air at high temperatures, a SiC- MoSi2/ZrO2-MoSi2 coating was prepared on the surface of C/C composites by pack cementation and slurry method. The microstructures and phase compositions of the coated C/C composites were analyzed by scanning electron microscopy and X-ray diffraction, respectively. The result shows that the SiC-MoSi2/ZrO2-MoSi2 coating is dense and crack-free with a thickness of 250-300 μm. The preparation and the high temperature oxidation property of the coated composites were investigated. The as-received coating has excellent oxidation protection ability and can protect C/C composites from oxidation for 260 h at 1773 K in air. The excellent anti-oxidation performance of the coating is considered to come from the formation of ZrSiO4, which improves the stability of the coating at high temperatures.

Effect of wear conditions on tribological properties of electrolessly-deposited Ni-P-Gr-SiC hybrid composite coating

The friction and wear properties of the electrolessly-deposited Ni-P-Gr-SiC composites were investigated. The effects of graphite content, load and rotation speed on the friction coefficient and wear resistance of the composite coatings were mainly investigated. The worn surface and cross section of the coatings were characterized by scanning electron microscopy and energy-dispersive X-ray analysis. The results show that the composite coatings reveal good antifriction and wear resistance due to the synergic effect of graphite and SiC particles. The formation of graphite-rich mechanically mixed layer （GRMML） on the surface of Ni-P-Gr-SiC coating contributes to the good tribological behavior of the wear counterparts and SiC particles play a load bearing role in protecting GRMML from shearing easily.

Preparation and tribological performances of Ni-P-multi-walled carbon nanotubes composite coatings

Multi-walled carbon nanotubes （MWNTs） were wet-milled in the presence of ammonia and cationic surfactant and then used as reinforcements to prepare Ni-P-MWNTs composite coatings by electroless plating. The tribological performances of the composite coatings under dry condition were investigated in comparison with 45 steel and conventional Ni-P coating, Micrographs show that short MWNTs with uniform length and open tips were obtained through the wet-milling process. The results of wear test reveal that the Ni-P-MWNTs composite coatings posses much better friction reduction and anti-wear performances when compared with 45 steel and Ni-P coating. Within the MWNTs content range of 0.74%-1.97%, the friction coefficient and the volume wear rate of the composite coatings decrease gradually and reach the minimum values of 0.08 and 6.22x10-15 m3/（N.m）, respectively. The excellent tribological performances of the composite coatings can be attributed to the introduction of MWNTs, which play both roles of reinforcements and solid lubricant during the wear process.

Erosion and Toughening Mechanisms of Electroless Ni-P-Nano-NiTi Composite Coatings on API X100 Steel under Single Particle Impact

The addition of superelastic NiTi to electroless Ni-P coating has been found to toughen the otherwise brittle coatings in static loading conditions, though its effect on erosion behaviour has not yet been explored. In the present study, spherical WC-Co erodent particles were used in single particle impact testing of Ni-P-nano-NiTi composite coatings on API X100 steel substrates at two average velocities—35 m/s and 52 m/s. Erosion tests were performed at impact angles of 30°, 45°, 60°, and 90°. The effect of NiTi concentration in the coating was also examined. Through examination of the impact craters and material response at various impact conditions, it was found that the presence of superelastic NiTi in the brittle Ni-P matrix hindered the propagation of cracks and provided a barrier to crack growth. The following toughening mechanisms were identified: crack bridging and deflection, micro-cracking, and transformation toughening.

Crystalline texture evolution, control of the tribocorrosion behavior, and significant enhancement of the abrasion properties of a Ni-P nanocomposite coating enhanced by zirconia nanoparticles

This paper describes an investigation of the effect of ZrO2 nanoparticles on the abrasive properties,crystalline texture developments,and tribocorrosion behavior of Ni-P nanostructured coatings.In the investigation,Ni-P and Ni-P-ZrO2 nanostructured coatings are deposited on St52 steel via the electroless method.Transmission electron microscopy(TEM),field emission scanning electron microscopy(FE-SEM),X-ray diffraction(XRD),energy dispersive spectroscopy(EDS),cyclic-static polarization tests in 3.5wt%NaCl solution,the tribocorrosion test(by back-and-forth wear in electrochemical cell),and the microhardness test using the Vickers method were performed to characterize and analyze the deposited coatings.The results of this study showed that the addition of ZrO2 nanoparticles to the Ni-P electroless bath produced the following:a sharp increase in wear and hardness resistance,the change of the wear mechanism from sheet to adhesive mode,the reduction of pitting corrosion resistance,significant reduction in the tribocorrosion protective properties,change in the preferred orientation of the crystalline texture coating from(111)to(200),increase in the sedimentation rate during the deposit process,and a sharp increase in the thickness of the Ni-P nanostructured coatings.

化学镀法制备Ni包覆ZrO_2粉末镀液的研究

研究了在未经预处理的ＺｒＯ２ 粉末表面镀覆金属Ｎｉ 的工艺．采用正交组合实验方法考查了影响大的几个主要因素对化学镀液稳定性和镀覆能力的影响，确定了保证一定镀覆能力下镀液稳定的最佳实验条件．

Ni-ZrO_2复合电镀工艺的研究

研究了Ni ZrO2 复合镀液体系中微粒与镀液间的相互作用。镀液中的电解质NiSO4和NiCl2 对ZrO2 纳米微粒在复合镀液中的悬浮稳定性有很大影响。阴极极化曲线表明纳米微粒的加入改变了基质金属电沉积的过程。以高分子聚电解质作为分散剂 ,利用其在微粒之间形成的空间位阻效应 ,减弱镀液中离子对微粒的聚沉作用 ,得到了均匀分散的ZrO2 纳米微粒的复合镀镍溶液 。

化学镀法制备Ni包覆ZrO_2微粉

采用共沉淀ｔ－ＺｒＯ２（１０％ＭｇＯ，以摩尔计）微粉为基体原料，用化学镀法制备了不同Ｎｉ含量的Ｎｉ包覆ＺｒＯ２复合微粉．由于采用了合适的络合剂和稳定剂，反应速度易于控制，且粉末不需活化处理即可施镀．运用ＸＲＤ、ＳＥＭ、ＥＰＡＸ等分析检测技术研究了粉体．结果表明，镀覆后颗粒均由Ｎｉ和ＺｒＯ２两种成份复合而成。

Ni-P-Zn_3(PO_4)_2(ZnSnO_3、ZnSiO_3)纳米复合化学镀层性质和组成的研究

研究了温度、时间、浓度等对 A3钢片上 Ni-P-Zn3(PO4)2、 Ni-P-ZnSnO3和 Ni-P-ZnSiO3纳米复合化学镀层外貌的影响。用扫描电子显微镜（ SEM）观察外貌；称重法测定厚度；通过 10％ NaCl溶液、 1％ H2S气体加速腐蚀试验、 10％ CuSO4溶液点滴试验等多种手段测定其耐腐蚀性能；用 X-射线光电子谱 (XPS)及俄歇电子能谱 (AES)测定其价态及组成。结果表明：在最佳施镀条件下，可得光亮、致密、耐腐蚀性强于 A3钢、磷化膜及 Ni-P镀层的纳米复合化学镀层。镀层的原子百分组成约为 (％ )： Ni-P-Zn3(PO4)2： Ni 70.00,P 12.47,Zn3(PO4)2 13.93,C 3.6； Ni-P-ZnSnO3： Ni 77.56,P 10.00,ZnSnO3 9.84,C 2.6； Ni-P-ZnSiO3： Ni 83.00,P 10.96,ZnSiO3 5.15,C 0.89。

Ni-ZrO_2复合镀层形成过程的研究

采用复合电沉积技术制备出了Ｎｉ－ＺｒＯ２复合镀层，并利用正交设计对影响复合电沉积过程的有关因素（包括电流密度、ＺｒＯ２微粒粒径、搅拌方式、镀液中微粒含量及其间的相互作用）进行了系统研究，镀液中ＺｒＯ２微粒表面荷电状况的分析表明，ＺｒＯ２微粒表面由于吸附了溶液中的Ｎｉ２＋而荷正电。

纳米Al_(2)O_(3)颗粒掺杂对化学镀Ni-Cu-P镀层耐蚀性的影响

为提高镀锌铁片表面化学镀层Ni-Cu-P的耐蚀性,在镀液中添加纳米Al_(2)O_(3)颗粒制备了Ni-Cu-P-Al_(2)O_(3)复合镀层。采用贴滤纸法、扫描电镜(SEM)及其附带的能谱仪(EDS)、电化学工作站对镀层孔隙率、表面形貌、元素含量及耐蚀性进行测试分析。结果表明,掺杂纳米Al_(2)O_(3)颗粒得到的Ni-Cu-P-Al_(2)O_(3)复合镀层相较于Ni-Cu-P镀层孔隙率降低了0.02 N/cm^(2)、腐蚀电流降低了2.01×10^(-8)A/cm^(2)、腐蚀电位正移了0.015 V。

纳米颗粒TiO_2化学复合镀层的功能特性

本文研究了化学镀Ni P TiO2 (纳米颗粒 )复合镀层的磁学性能和光催化性能。实验结果显示 ,纳米颗粒化学复合镀层是较好的高耐磨软磁材料 ;其光催化性能和粉体纳米TiO2 不相上下。这些优越的性能展示了纳米颗粒复合镀层具有良好的应用前景。

ZTA陶瓷颗粒表面Ni-TiB_(2)镀层的制备及工艺优化

为了解决氧化锆增韧氧化铝(ZTA)陶瓷颗粒增强铁基复合材料制备过程中,ZTA陶瓷颗粒与铁基体润湿性差的问题,在ZTA陶瓷颗粒表面镀覆Ni-TiB_(2)镀层。通过化学镀镍及电镀Ni-TiB_(2)两步法,先在ZTA陶瓷颗粒表面化学镀镍得到具有导电性的ZTA@Ni颗粒,再在ZTA@Ni颗粒表面电镀均匀的Ni-TiB_(2)复合镀层。采用XRD对ZTA、ZTA@Ni和ZTA@Ni-TiB_(2)颗粒进行物相分析;使用数码相机和SEM分别对ZTA、ZTA@Ni和ZTA@Ni-TiB_(2)颗粒进行宏观及微观形貌观察;并利用EDS分析镀层中各个元素的质量百分比。分别研究电镀液中TiB_(2)粉末浓度、氯化胆碱-乙二醇(ChCl-EG)浓度及沉积电压3种因素对Ni-TiB_(2)复合镀层的成分及表面形貌的影响。结果表明,在1.8 V的沉积电压下,TiB_(2)粉末掺杂浓度为6 g/L,ChCl-EG的浓度为9 g/L时,Ni-TiB_(2)复合镀层平整均匀,无孔洞产生,镀层中的TiB_(2)质量百分数可以达到58.22%~64.79%。

基于RSM-BBD的Ni-Cu-P/CeO_(2)镀层的制备与性能

在化学镀Ni-Cu-P三元镀层的基础上,向镀液中加入CeO_(2)纳米颗粒,并采用响应面实验设计(RSM-BBD)进行镀液配方优化,利用最佳的配方制备了Ni-Cu-P/CeO_(2)复合镀层。采用扫描电镜(SEM)、能谱仪(EDS)、X射线衍射仪(XRD)、电化学工作站和显微硬度仪等研究了复合镀层的表面形貌、微观组织结构、耐蚀性以及硬度。结果表明:Ni-Cu-P镀层和Ni-Cu-P/CeO_(2)复合镀层的表面光滑平整,没有胞状颗粒,复合镀层中有CeO_(2)颗粒镶嵌在其中,且复合镀层的晶粒更细小更致密;Ni-Cu-P镀层的硬度和孔隙率分别为479.1 HV0.1和0.12,加入CeO_(2)颗粒后复合镀层的硬度增加,孔隙率更低,分别为678.7 HV0.1和0.04;极化曲线测试结果表明,Ni-Cu-P/CeO_(2)复合镀层的耐蚀性比Ni-Cu-P镀层的耐蚀性更好,其腐蚀电位和腐蚀电流密度分别为-0.559 V和7.943×10^(-8)A·cm^(-2)。

三元配位体系对低磷复合化学镀镍-磷-纳米二氧化钛的影响

低磷复合化学镀镍层具有优异的耐碱腐蚀性和超高的硬度,但尚未应用到规模化生产中。以沉积速率、镀层磷含量、硬度及孔隙率为评价指标,在乳酸-丙酸二元配位剂的基础上,分别研究了采用三乙醇胺、苹果酸、丁二酸、乙二胺作为辅助配位剂时对低磷复合化学镀镍-磷-纳米二氧化钛的影响。镀液的基础配方和工艺条件为:NaH_(2)PO_(2)·H_(2)O_(2)3 g/L,NiSO_(4)·6H_(2)O_(2)8 g/L,辅助配位剂适量,乳酸18 mL/L,丙酸4 mL/L,CH 3 COONa·3H_(2)O 15 g/L,十二烷基苯磺酸钠(SDBS)40 mg/L,pH值4.8±0.2,温度(85±2)℃,施镀时间1 h。结果表明:采用乙二胺作为辅助配位剂时,镀层的综合性能良好。当乙二胺的用量为4 mL/L时,镀速为23.62μm/h,镀层磷含量为3.53%,镀层镀态硬度为561.4 HV,孔隙率为0.35个/cm 2。

化学复合镀Ni-Mo-P/CeO_(2)镀层结构与摩擦学性能研究

为研究CeO_(2)稀土添加对Ni-Mo-P化学镀层结构及性能的影响,采用化学复合镀技术,在GH4169镍基高温合金表面制备Ni-Mo-P镀层、Ni-Mo-P/CeO_(2)复合镀层,并对其进行400℃热处理。利用SEM、EDS、XRD对镀层组织结构、元素组成、相结构进行分析。采用显微硬度计、纳米压痕仪、球-盘式摩擦磨损试验机、三维表面轮廓仪对镀层力学性能和摩擦学性能进行分析。结果表明:Ni-Mo-P镀层分布有典型的球状结构,为纳米晶和非晶混合的混晶态结构,结晶化程度只有16%。加入CeO_(2)颗粒后Ni-Mo-P/CeO_(2)复合镀层内分布有孔洞,镀层粗糙度增加,镀层结晶化程度提高至51%。400℃热处理后镀层内析出纳米晶Ni_(3)P相,镀层结晶度增大,镀层内孔洞消失,组织致密度获得改善。添加CeO_(2)颗粒使镀层的硬度有所降低,热处理可明显提高镀层的硬度;热处理后Ni-Mo-P镀层硬度(HV)从镀态的6321 MPa上升至13504 MPa,Ni-Mo-P/CeO_(2)复合镀层硬度(HV)由镀态的5351 MPa提高至11182 MPa。400℃热处理可以明显提高镀层的耐磨性能;CeO_(2)颗粒的添加提高了镀层的韧性,抑制了磨损过程中裂纹的产生,使得复合镀层具有优良的耐磨性能。