Laser surface alloying of silumin

Laser alloying is an effective way to increase the surface hardness and wear resistance of materials, including aluminum. The effect of laser alloying on the structure and hardness of silumin AL30, which is used to produce engine pistons operating at high temperatures, is an interesting subject for study.Translated from Metallovedenie i Tremicheskaya Obrabotka Metallov, No. 2, pp. 18 – 19, February, 1995.     

Properties of silumins produced by alloying with glass microspheres

Conclusions Inoculation of Al–Si alloys with hollow glass microspheres causes an increase in their strength and plasticity. In contrast to silumins such alloys may be wrought and it is possible to obtain the profiles and thereby to broaden the possibilities of their use.Nikolaev Shipbuilding Institute. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 12, pp. 46–47, December, 1989.     

Laser alloying

Conclusion Laser alloying is one of the promising methods of improving the wear resistance of parts. Alloyed layers containing boride, carbide, nitride, and oxide phases have the highest wear resistance. In the selection of the regime of laser alloying for actual parts the scale factor has to be taken into account. The most promising for laser alloying are continuous CO₂ lasers.Belorussian Polytechnic Institute, Mogilev Technological Institute. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 3, pp. 14–19, March, 1987.     

铝合金表面多层复合纳米碳管/钛的激光合金化

在铝合金表面使用真空镀的方法形成CNT8／Ti／AL／…多层复合，经激光合金化形成复合涂层。利用X射线衍射、扫描电镜对复合层相构成及微观组织进行了分析。结果表明，复合层中存在着TiC颗粒和碳纳米管CNTs；CNTs仍保留其原有的管状结构，且在复合层中相互缠绕呈网状均匀弥散分布；反应原位合成的TiC颗粒尺寸均匀细小，附着于CNTs上从而改善了CNTs与基体之间的结合性能；复合涂层已合金化，与基体的界面为冶金结合。     

Laser surface alloying of ferritic Fe-40Cr alloy with ruthenium

An investigation is made of the laser surface alloying of an experimental ferritic Fe-40Cr alloy with a rutherium powder coating using a continuous wave CO₂ laser. Themicrostructure and corrosion behaviour of the laser surface alloying layer and the Fe-40Cr bulk allyo were examined by means of scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy, microhardness, potentiodynamic and corrosion potential measurements. The results of the microstructural examination showed that fine cellular dendrites with a ruthenium content as high as 51.84wt.% were produced by laser surface alloying. The extended solubility of ruthenium in the cellular dendrites resulted in a dramatic increase of the hardness in the laser alloying layer. Potentiodynamic and open circuit corrosion potential measurements indicated that the ruthenium-containing surface layer spontaneously passivated in hydrochloric and sulphuric acid solutions, whereas the bulk Fe—40Cr alloy remained in the active state when exposed in these reducing acid solutions.     

Laser surface hardening of martensitic stainless steel hollow parts

This paper deals with numerical simulation and experimental validation of laser heat treatment of an industrial axisymmetric hollow mechanical part by means of a strategy based on helical tracks. This component, made of AISI 420B martensitic stainless steel, features a low wall thickness and, according to this, it is not easily treatable by means of laser surface hardening. The work carried out was aimed at demonstrating that numerical simulation allows a drastic reduction of the experimental activity and that it makes possible to prove a very high sensitivity of the results to process parameters variation.     

Laser surface alloying fabricated porous coating on NiTi shape memory alloy

Laser surface alloying technique was applied to fabricate a metallic porous coating on a solid NiTi shape memory alloy. By laser surface alloying a 40%TiH2-60%NiTi powder mixture on the surface of NiTi alloy using optimized laser process parameters, a porous but crack-free NiTi layer can be fabricated on the NiTi substrate. The porous coating is metallurgically bonded to the substrate NiTi alloy. The pores are uniformly distributed and are interconnected with each other in the coating. An average pore size of less than 10μm is achieved. The Ni content of the porous layer is much less than that of the original NiTi surface. The existence of the porous coating on the NiTi alloy causes a 37% reduction of the tensile strength and 55% reduction of the strain as compared with the NiTi alloy. Possible biomedical or other applications for this porous surface with good mechanical strength provided by the substrate are prospective.     

铸造铝合金预置Si粉激光表面合金化研究

为了改善铸造铝合金的表面性能,以Si粉作为预置涂层材料,采用高功率CO2,激光器进行表面合金化处理,在A357铸造铝合金表面制备了未熔Si颗粒均匀分布的高硅A1-Si合金涂层,整个涂层组织致密、无气孔、无裂纹,在油润滑条件下测试了激光表面合金化层的耐磨性.结果表明,激光表面合金化处理后A357合金表面改性层的维氏硬度和耐磨性均得到显著提高.     

Electrode materials for electrospark alloying of machine parts

The conditions of producing tungsten alloys with chromium and molybdenum by thermal reduction methods of a scheelite concentrate with the additions of oxides of alloying elements are studied. The application of W–Cr and W–Cr–Mo alloys for electrospark alloying of the surface of machine parts increases the wear resistance of the parts 1.5–2 times.     

不锈钢增材制造件表面缺陷激光超声检测

利用激光超声技术检测增材制造件表面缺陷,采用有限元方法模拟热弹机制下激光激发超声波的传播过程,对不同探测位置接收的表面波反射信号进行了分析,研究缺陷的深度和宽度对表面波反射信号的影响。对316L不锈钢增材制造件进行了激光超声检测试验,验证了该模型的正确性。利用小波软阈值去噪算法处理采集到的激光超声信号。结果表明,数值模拟与试验结果基本一致,表面波与缺陷作用产生的RS波和RR波的到达时间差可以检测缺陷的深度,缺陷的宽度对检测结果几乎无影响。     

纯钛表面Zr-N等离子合金化(英文)

为了改善纯钛的表面性能,利用等离子表面合金化技术在纯钛表面形成Zr-N改性层。对Zr-N改性层的微结构、成分及硬度进行测试,并对改性层形成及表面硬度提高的机理进行分析。利用球-盘磨损试验对表面改性纯钛的摩擦学性能进行研究。结果表明,在纯钛表面形成了均匀致密的Zr-N改性层,改性层由表面Zr-N化合物层和基体内Zr、N的扩散层构成。Zr-N表面改性层显著提高了纯钛的表面硬度,表层的最高硬度约为HK1040。Zr-N表面改性层没有减摩效果,但明显改善了纯钛的磨损性能。     

Laser alloying of aluminium alloys with chromium

The microstructure and corrosion resistance of laser-alloyed aluminium and ANSI 7175 aluminium alloy with chromium were investigated. Surface layers alloyed with chromium contain relatively large amounts of intermetallic compounds dispersed in a matrix of -Al. The intermetallic compound particles present needle-like morphologies, organized in a dense network or distributed radially. Al₇Cr, Al₁₁Cr₂ and -Al phases have been identified by X-ray diffraction. The alloyed layers may contain cracks, pores, inclusions and undissolved chromium particles, depending on the chromium concentration and the particle size. However, homogeneous layers were produced by a two-step process, consisting of laser alloying followed by remelting. The second treatment eliminates porosity and refines the structure. The hardness attains a Vickers hardness of 155 HV in chromium-alloyed aluminium and exceeds 300 HV in chromium-alloyed 7175. The corrosion behaviour of the above alloys was assessed using anodic polarization techniques. Laser alloying of aluminium and 7175 with chromium improves the pitting corrosion resistance of the alloys. The effect depends on the chromium content of the alloyed layers and is more significant in 7175 alloy.     

Formation of wear-resistant graphitized layers on the surface of parts from iron and titanium alloys by the method of electric spark alloying

The process of formation of free graphite in the surface layer of specimens from alloys based on iron and titanium by the method of electric spark alloying is described. It is established that a high content of free graphite in the surface layer can be obtained only by feeding it in a powder form (together with the modifying materials) into the zone of electric spark treatment. The wear resistance of the thus graphitized surface layers of steel and titanium alloy specimens increases by a factor of 7–8. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov. No. 7, pp. 23–26, July, 2000.