Effect of silicon on formation of boride coatings

Conclusions In the process of boriding, silicon is forced into the transition zone and has an inhibiting effect on the growth of the high-boron phase (FeB) and the layer of borides, leading to a change in the phase composition of this zone.Kiev Polytechnical Institute. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 3, pp. 67–68, March, 1973.     

Structural properties of boride coatings for triboengineering

Boride coatings on steels of different classes are rather widely used for decreasing the intensity of abrasive wear and thermal degradation of the surface of machine parts and equipment. Borating can also be an efficient means for increasing the wear resistance of heavily loaded friction units. The present work presents results of an investigation of the structure and wear resistance of boride coatings on steel 15N3MA. The optimum structure of the boride layer and the range of application of boride coatings are determined.Translated from Metallovedenie i Termicheskaya Obralbotka Metallov, No. 6, pp. 35–38, June, 1995.     

Characterization of boride coatings on a ductile cast iron

In this work, the EN-GJS-400-15 cast iron was pack-borided in a powder mixture composed of 5% B₄C, 5% NaBF₄ and 90% SiC at the three temperatures: 900, 950 and 1000°C for 2, 4 and 6 h, respectively. The pack-borided EN-GJS-400-15 cast iron was characterized by the following experimental techniques: optical microscopy, XRD analysis and Microhardness Vickers tester. The growth kinetics of boride layers was also investigated. As a consequence, the boron activation energy was found to be 212.28 kJ mol^–1 for the EN-GJS-400-15 cast iron. Based on a regression model, a useful equation was derived to estimate the boride layer thickness as a function of the boriding parameters (time and temperature). A good agreement was then obtained between the predicted values of boride layers thicknesses and those measured experimentally. In addition, an iso-thickness diagram was proposed to be used as a simple tool to select the boride layers thicknesses according to the potential applications of EN-GJS-400-15 cast iron in industry.     

原位合成的硼化物类高温陶瓷涂层的研究

采用等离子弧堆焊设备，通过钛合金和硼合金粉末之间的高温冶金反应，在普通碳钢表面制备了合TiB2的金属陶瓷层。试验结果表明：通过改变B4C含量，可得到不同的组织，并且随着B4C含量增加，基体组织中Fe2B数目也增加，强化基体，使堆焊层上表面硬度增加。     

镁热还原自蔓延高温合成硼化钛微粉的动力学

应用DTA技术分别测定了Mg与TiO2,Mg与B2O3及Mg与TiO2和B2O3之间的多相反应,分析了Mg,TiO2和B2O3三相可能存在的反应机制,应用Freeman-Carroll法和Kissinger法计算了反应的活化能和反应级数。结果表明Mg-B2O3-TiO2之间的反应为复杂的固-液-液反应,TiO2与Mg之间的固-液反应放出的强大热量诱发了B2O3和Mg之间的液-液反应,而Ti与B间的反应放出的热量反过来又促进前两者的反应。表观活化能在温度段760～858℃为E1=297kJ·mol-1,相应的反应级数分别为n1=0.8。采用Kissinger法计算的反应级数为0.9,与Freeman-Carroll法所得的n1=0.8基本一致。     

High-temperature oxidation of titanium silicide coatings on titanium

Coatings of Ti ₅Si₃ on titanium have been prepared by means of decomposition of silane SiH₄ on heated titanium ribbons. Oxidation of the coated titanium specimens was much slower than that of the noncoated ones. Gravimetric and morphological experiments allowed to propose a mechanism describing the oxidation process.     

Intermetallic protective coatings on titanium

In the presented work, the powder siliconizing and liquid phase alloying were used for a surface hardening of titanium and to protect titanium against high-temperature oxidation. The powder siliconizing was carried out in a pure Si powder at 900–1100 °C/3–48 h and the liquid phase alloying was realized in an Al–20 wt.% Si melt at 800 °C/5–40 min. It was shown that the coating methods produced hard multi-phase surface layers composed of various kinds of silicides (Ti₅Si₃, Ti₃Si and TiSi) and ternary Ti(Al_XSi_1−X)₂ (τ₂) phase. The binary silicide layers grew in accordance with the parabolic law while the ternary layer grew very rapidly. It was shown that the powder siliconizing at 900–1100 °C/3 h produced sufficiently thick and compact protective layers. The liquid phase alloying at 800 °C/10 min was efficient for preparation of protective layers. The oxidation experiments were conducted at 850 °C in air. Both the powder siliconized and liquid phase alloyed coatings were shown to provide a good protection against high-temperature oxidation.     

激光功率对钛合金表面Ni基复合涂层的影响

采用光纤激光器,在Ti6Al4V合金表面激光熔覆Ni60和Ni/MoS2粉末制备复合涂层,利用OM、SEM、EDS分析了激光功率对熔覆层宏观形貌、显微组织、显微硬度的影响。结果表明,在其他工艺参数不变的条件下,随着激光功率的增大,熔覆层宽度、厚度、基材熔化深度、热影响区深度均增大;显微硬度逐渐增大;熔覆层表面质量下降,最佳激光功率范围为1.5~2 kW。