Degradation failure features of chromium-plated gun barrels with a laser-discrete-quenched substrate

The effect of substrate laser-discrete quenching on the degradation failure of chromium-plated gun barrels was metallurgically investigated. The results show that substrate laser-discrete quenching changes the failure patterns of chromium coatings during firing, and some periodic through-thickness cracks in the fired chromium coatings are justly located at original substrate zones between two adjacent laser-quenched tracks. Moreover, chromium coatings and the laser-quenched zones on the substrate are simultaneously degraded in microstructure and property during firing. Furthermore, the periodic structure of the laser-discrete-quenched steel (LDQS) substrate near the breech remains after firing, and the hardness of the fired laser-quenched zones is still higher than that of original substrates. The specific failure features were utilized to illustrate the mechanism of the extended service life of chromium-plated gun barrels with the LDQS substrate. (c) 2007 Elsevier B.V All rights reserved

Characteristics of the interface of a laser-quenched steel substrate and chromium electroplate

The interface of a laser-discrete-quenched steel substrate and as-deposited chromium electroplate was investigated by ion beam etching, dissolving-substrate-away and using a Vickers microhardness tester, in an attempt to reveal the mechanism that the service life of the chromium-coated parts is increased by the duplex technique of laser pre-quenching plus chromium post-depositing. The laser quenching of the steel substrate can reduce the steep hardness gradient at the substrate/chromium interface and improve the load-bearing capacity of chromium electroplate. Moreover, the laser quenching prior to plating has an extremely great effect on the morphologies and microstructure of the substrate/chromium interface: there is a transient interlayer at the original substrate/chromium interface while there is not at the laser-quenchedzone/chromium interface; the near-substrate surface microstructure and morphologies of the free-standing chromium electrodeposits, whose substrate was dissolved away with nital 30% in volume, inherit the periodically gradient characteristics of the laser-discrete-quenched substrate surface. (c) 2006 Elsevier B.V. All rights reserved

某型舰炮身管表面锈蚀机理

针对舰炮身管表面镀铬层出现剥落、散在无规则及深浅不均的锈坑现象,对舰炮身管表面锈蚀机理进行研究。通过对样件锈蚀表面宏观形貌及微观腐蚀形貌观察,结合锈蚀坑分布规律统计分析,得出镀铬层的开裂剥落是造成身管锈蚀的根本原因。实验结果表明:腐蚀介质抵达基体界面,形成锈蚀源,其中氯离子起到先锋作用;镀铬层鼓泡以及蚀坑扩张时的铬层断裂,均为固支弯曲断裂模式。该研究可为舰炮身管表面防腐蚀及锈蚀修复方法提供参考依据

脉冲激光熔化过程热物理特性的有限元分析

利用热黏流体-刚性导热体二维轴对称模型,采用混合有限元方法,研究了脉冲激光熔化过程中熔池的非线性、非稳态、复杂的超常热物理过程,对熔池温度场、温度梯度场、流场和压力场等过程参数进行了数值计算。研究结果表明,熔池中形成上部区域以对流传热机制为主,底部区域以导热热传导机制为主的传热模式:熔地中温度场、温度梯度场、流场和压力场参数均随脉冲激光作用时间和空间位置变化

激光表面强韧化加工技术与应用

由于国民经济和国防建设的不断发展,许多重大装备和设备的关键零部件的工况日趋苛刻和严酷。强化表面是改善这类零部件使用效果和使用寿命最直接、最经济和最有效的措施,但是实践表明,采用常规的表面处理(如表面淬火和表面渗、镀等)方法,除强化效果难以满足不断提高的使用要求外,材料强度与韧性之间难以协调的矛盾也是工件使用寿命进一

合金铸铁热轧辊材料的激光熔凝组织及抗磨损性能

研究了合金铸铁热轧辊材料的激光熔凝组织及磨损性能，实验观察到熔凝区存在奥氏体及碳化物的二类枝晶结构，熔凝组织由马氏体，残余奥氏体及碳化物组成，晶粒明显细化，并在次表层出现超细晶区及残余奥氏体的非均匀分布特征，与常规组织相比，熔凝区的显微硬度、抗回火稳定性及磨损性能均明显提高

激光快速熔凝中的主要热物理问题

本文讨论了激光快速熔凝过程中存在的主要热处理问题及现象，主要内容包括材料对激光的吸收，固态及液态热传导中热物理参数的确定，影响对流的主要因素，以及凝固的特点

Study of Laser Oxidizing for Titanium Hardening

研究了钛及其合金的激光渗氧硬化方法。对工业纯钛的初步试验结果表明,用激光进行固态扩散渗氧处理可以明显改变钛表层组织、硬度和耐磨性。该方法在某零件上的试用效果良好