Cavitation erosion behavior of WC coatings on CrNiMo stainless steel by laser alloying

The WC powder was precoated on the surface of CrNiMo stainless steel and then made into an alloying layer by using the laser alloying technique. Phases in the layers were investigated by X-ray diffraction （XRD） analysis and surface morphologies after cavitation erosion were observed with the help of scanning electron microscopy （SEM）. The cavitation erosion behavior of the CrNiMo stainless steel and WC laser alloying layer in distilled water was tested with the help of ultrasonic vibration cavitation erosion equipment. The results showed that the thickness of the laser alloying layer was about 0.13 mm. The layer had a dense microstructure, metallurgically bonded to the substrate, and no crack had been found. The cavitation erosion mass loss rate of the laser alloying layer was only 2/5 that of the CrNiMo stainless steel. The layer had better cavitation resistance properties because of its metallurgical combination and the strengthening effects of the precipitate phases.

Effect of surface damage induced by cavitation erosion on pitting and passive behaviors of 304L stainless steel

The corrosion behavior of 304L stainless steel(SS)in 3.5wt%NaCl solution after different cavitation erosion(CE)times was mainly evaluated using electrochemical noise and potentiostatic polarization techniques.It was found that the antagonism effect resulting in the passivation and depassivation of 304L SS had significant distinctions at different CE periods.The passive behavior was predominant during the incubation period of CE where the metastable pitting initiated at the surface of 304L SS.Over the rising period of CE,the 304L SS experienced a transition from passivation to depassivation,leading to the massive growth of metastable pitting and stable pitting.The depassivation of304L SS was found to be dominant at the stable period of CE where serious localized corrosion occurred.

Cavitation Erosion Behavior of CrMnN Duplex Stainless Steel in Distilled Water and 3% NaCl Solution

The cavitation erosion (CE) behavior of CrMnIM ferrite-austenite duplex stainless steel in distilled water and 3% NaCI solution was investigated by using a magnetostrictive-induced CE facility. The damaged surfaces were observed by scanning electron microscope (SEM). It was found that the CE resistance of CrMnN steel was higher than that of OCrl3Ni5Mo steel. The mass loss rate of CrMnN steel in distilled water was similar to that in 3% NaCI except at the early stage of CE. The failure mode of ferrite phase was brittle fracture, which had adverse effect on the resistance to CE, while the failure of austenite phase was a ductile failure in CrMnN steel. The excellent resistance to CE was related to the good mechanical properties of austenitic phase and the consumption of CE energy by plastic deformation involving slip and twinning.

Cavitation erosion resistance of 316L stainless steel fabricated using selective laser melting

Cavitation erosion degrades the performance and reliability of hydraulic machinery.Selective laser melting(SLM)is a type of metal additive manufacturing technology that can fabricate metal parts directly and provide lightweight design in various industrial applications.However,the cavitation erosion behaviors of SLM-fabricated parts have rarely been studied.In this study,SLM 316L stainless steel samples were fabricated via SLM technology considering the scanning strategy,scanning speed,laser power,and build orientation.The effect of the process parameters on the cavitation erosion resistance of the SLM-fabricated 316L stainless steel samples was illustrated using an ultrasonic vibratory cavitation system.The mass loss and surface topography were employed to evaluate the surface cavitation damage of the SLM-fabricated 316L stainless steel samples after the cavitation test.The cavitation damage mechanism of the SLM-fabricated samples was discussed.The results show that the degree of cavitation damage of the sample fabricated via SLM with a few defects,anisotropic build direction,and columnar microstructure is significantly decreased.Defects such as pores,which are attributed to low laser power and high scanning speed,may severely aggravate the cavitation damage of the SLM-fabricated samples.The sample fabricated via SLM with a low laser power and exposure time exhibited the highest porosity and poor cavitation erosion resistance.The cellular structures are more prone to cavitation damage compared with the columnar structures.A sample with a high density of grain boundaries will severely suffer cavitation damage.

Study on prediction model of cavitation erosion incubation period of duplex stainless steel surfacing layer in a benign medium

In order to estimate the cavitation incubation period of duplex stainless steel(DSS)under ultrasonic cavitation erosion(CE),this paper analyzed the loading process of material during ultrasonic CE.Local strain theory,cumulative damage theory,and Bernoulli probability model were used to derive the minimum number of cavitation impacts required for the initiation of fatigue cracks,and the predictive equation of the material cavitation incubation period was given.DSS was obtained by tungsten inert gas welding(TIG)powder surfacing method.Tensile test and ultrasonic CE test were performed,and the tensile test data were used to calculate the cavitation incubation period by using the predictive equation.Due to the possible presence of precipitates and micro-cracks in the sample,there was an error between the calculated and the test results.The results showed that the max error between the calculated results and the test results was 8.1%,and the errors of the remaining two groups were within 3.5%.

清水和含沙水中20SiMn和0Cr13Ni5Mo钢的空蚀行为

利用超声振荡空蚀实验机对两种主要的水轮机用金属材料进行了清水和含沙水条件下的空蚀行为研究．结果表明，高 硬度的０Ｃｒ１３Ｎｉ５Ｍｏ不锈钢抗清水和含沙水的空蚀性能均显著高于低硬度的２０ＳｉＭｎ低合金钢．在清水空蚀中０Ｃｒ１３Ｎｉ５Ｍｏ 不锈钢均匀脱落，而 ２０ＳｉＭｎ低合金钢不均匀脱落，表面出现明显的空蚀坑.空蚀和沙子冲蚀磨损的联合作用使得两种材料在含 沙水中的空蚀失重显著高于清水空蚀． ０Ｃｒ１３Ｎｉ５Ｍｏ不锈钢在含沙水中的空蚀孕育期显著缩短．

Cr-Mn-N奥氏体-铁素体不锈钢的空蚀行为

利用超声振荡空蚀实验机对Cr-Mn-N奥氏体-铁素体不锈钢进行了空蚀研究.结果表明,低硬度Cr—Mn—N不锈钢的抗空蚀性能高于高硬度的0Cr13Ni5Mo不锈钢.空蚀过程中, Cr—Mn—N奥氏体-铁素体不锈钢中的铁素体优先脱落,空蚀表面的铁素体含量由19％迅速降低到6.9％后保持稳定.奥氏体易于在铁素体脱离后形成的蚀坑处开始脱落.加工硬化是该不锈钢吸收空蚀冲击能量的一个重要途径,是其硬度较低却表现出良好抗空蚀性能的重要原因.

不锈钢表面激光熔覆抗空蚀涂层技术研究进展

综述了国内外不锈钢抗空蚀激光表面熔覆技术的研究现状,介绍了该技术的特点,设备和抗空蚀熔覆粉末体系。并对激光熔覆层结构及性能作了较详细的介绍,阐述了熔覆层的抗空蚀性、耐磨蚀性和耐腐蚀性等。还简要介绍了该技术的应用现状,并提出了其今后的发展前景及方向。

不锈钢在氯化物介质中的空泡腐蚀行为及机理

利用空泡腐蚀试验仪,采用失重法、SEM及电化学方法,研究了1Cr18Ni9Ti不锈钢在氯化物介质中的空蚀行为及机理.结果表明:随着NaCl盐浓度的增大,空蚀速度增大;随着温度增加,空蚀速度先增大后减小,说明氯化物介质的腐蚀性对材料空蚀行为影响显著.极化曲线的测定表明,在不锈钢空泡腐蚀过程中,电极受阴阳极反应过程的混合控制.通过外加阴极电流,可以使材料空蚀速度显著降低,这表明在氯化物介质中,腐蚀电化学因素对材料的空蚀过程起重要作用.

大型水轮机叶片马氏体不锈钢的超声空蚀行为

利用超声振荡空蚀设备研究了一种大型水轮机马氏体不锈钢合金成分调整前后在蒸馏水和模拟长江水中的空蚀行为.观察空蚀表面形貌,结合力学性能,与普通13-4不锈钢进行对比分析.研究结果表明:3种不锈钢的显微组织由马氏体、铁素体和残余奥氏体组成;降低C,S,Si增加Ni,Mo,Mn并且经过精炼工艺改进后,不锈钢抗空蚀能力高于原合金和13-4不锈钢.调整后不锈钢的空蚀稳定期失重率小于7 mg/h,仅约为原合金的75%和13-4不锈钢的25%.在空蚀过程中,较软的铁素体相首先脱落,其次是较硬的马氏体相,并且观察到了清晰的空蚀表面疲劳源形貌.

CrNiMo不锈钢激光熔覆NiCrSiB涂层空蚀行为

应用激光熔覆法,采用镍基NiCrSiB合金粉末在CrNiMo不锈钢表面制作熔覆涂层。利用X射线衍射仪分析熔覆层的相组成;利用超声震荡空蚀实验机对熔覆层的空蚀行为进行研究;利用扫描电镜观察空蚀形貌。结果表明,所制得熔覆层组织均一、致密,与基体形成良好的冶金结合。抗空蚀能力提高到CrNiMo不锈钢基体的3倍。熔覆层抗空蚀能力增强的主要原因是熔覆层与基体良好的冶金结合、镍铬合金本身的良好性能和硼化物、硼碳化物等析出相的强化作用。

新型铬锰氮不锈钢的抗气蚀性能

在磁致伸缩仪和转盘气蚀仪上测试了一类新型的铬锰氮不锈钢的抗气蚀性能，并用Ｍｏｓｂａｕｅｒ谱分析了气蚀前后试样表层显微组织的变化。结果表明，铬锰氮双相（Ａ－Ｍ）不锈钢具有比目前水轮机转轮及叶片常用的ＺＧ０Ｃｒ１３Ｎｉ４～６Ｍｏ和ＺＧ０Ｃｒ１６Ｎｉ５Ｍｏ钢更高的抗气蚀性能，介稳奥氏体及其在气蚀过程中的组织变化是该类铬锰氮不锈钢具有优异的抗气蚀性能的重要原因。

Cr-Ni-Co奥氏体堆焊材料的空泡腐蚀行为

采用一种新型的Cr-Ni-Co奥氏体堆焊材料用钨极氩弧焊(TIG)堆焊到304不锈钢表面,将堆焊层与304不锈钢基体做对比,在人工海水的条件下利用超声波振动设备对两种材料进行耐空泡腐蚀试验,用失重法评价两种材料的抗空蚀性能,对Cr-Ni-Co堆焊层不同时间的空蚀形貌用扫描电镜(SEM)进行跟踪观测.结果表明,与304不锈钢的失重相比,Cr-Ni-Co堆焊层的失重显得很小,表现出优良的抗空蚀性能;从SEM观测到的形貌图的变化中看出滑移和相变是Cr-Ni-Co堆焊层吸收空泡冲击能的主要方式,应力集中使得材料易产生裂纹,进而导致材料的断裂和剥落.

不锈钢板中锰、钛、铝、铌夹杂物的原位统计分布分析

采用金属原位统计分布分析技术研究了系列不锈钢板中Mn,Ti,Al,Nb等类夹杂物存在的类型及状态,夹杂物的含量、组成、尺寸及位置分布等。该系列不锈钢样品中,各夹杂元素的分布具有不同的特点:Mn元素的大颗粒夹杂多位于板的中心部位;Ti,Al夹杂在整个横截面内分布则比较均匀;Nb大颗粒夹杂倾向于板的上、下表面附近及中心处。通道合成技术研究表明:Mn夹杂颗粒主要以硫化锰的形式存在;Ti夹杂主要以碳硫化钛的形式存在。给出了各类夹杂物的含量、粒度分布、平均粒径及20μm以上大颗粒夹杂的比例。综合分析和评价了各样品中夹杂物存在的种类及数量。该原位统计分布分析方法应用于不锈钢板中夹杂物的分析结果与传统的方法如金相、扫描电境等具有很好的一致性。

一种无镍奥氏体不锈钢的组织与性能

对用中频感应炉熔炼,电渣二次重溶工艺制备的Fe-Cr-Mn-C-N无镍奥氏体不锈钢进行了组织与性能测试。结果表明,该钢为单相奥氏体,平均晶粒直径为85μm,钢中成分均匀,未发现元素偏析;该钢具有较好的强度和韧性σb=1205MPa,σ0.2=632MPa,δ5=39%,HV=296。

Ni60喷焊层与ZG06Cr13Ni5Mo抗气蚀性能的研究

采用火焰喷焊法在低碳钢试样表面制备了N i 60喷焊层,与水力机械材料ZG06Cr13N i5Mo的抗气蚀性能进行对比。借助光学显微镜、X射线衍射仪、显微硬度计、磁致伸缩气蚀仪等设备对涂层的组织、结构和性能进行了研究,利用扫描电镜对气蚀形貌进行了观察。结果表明:N i 60喷焊层组织较细,显微硬度远高于ZG06Cr13N i5Mo;其抗气蚀性能和ZG06Cr13N i5Mo相比有所提高。

Cr-Ni型水轮机材料电化学腐蚀和抗空蚀行为

以ZG20Cr13为对比材料,在浓度为1mol/L的H2SO4溶液中测定了ZG06Cr13Ni4Mo(简称13-4)和Cr含量降至10.61%、8.34%和6.64%(mass)时材料的阳极极化曲线.利用超声振荡空蚀实验机和洛氏硬度计分别研究了13-4、8.5Cr-4Ni(简称8.5-4)和高强韧性Cr-Ni型不锈钢SRIF的空蚀行为和局域弹性性质,并研究了试验材料的组织和力学性能.结果表明,随13-4中Cr含量降低,材料的电化学腐蚀性能降低.当Cr含量降低至8.34%时,材料的电化学腐蚀性能与ZG20Cr13相当,仍属于不锈钢范畴.8.5-4、13-4和SRIF的局域弹性性质he无明显差别,13-4的抗空蚀性能略高于8.5-4,SRIF的抗空蚀性能明显高于前两者.

不锈钢空蚀磨蚀的形貌特征研究

本文利用转盘、高头水洞、ＳＥＭ、光学金相、ＥＤＡＸ和波谱等研究了奥氏体不锈钢表面发生纯空蚀、纯磨蚀、空蚀磨蚀共存、静水和动水腐蚀的形貌特征以及某些奇特现象；分析对比了黄河水轮机叶片的原体形貌；讨论了空蚀的机制。

亚稳奥氏体金属抗空蚀性能及其主要控制因素

用旋转圆盘实验机对5种亚稳奥氏体金属的抗空蚀性能和水轮机叶片用0Cr13Ni5Mo不锈钢进行了对比研究.结果表明, 2种应力诱发马氏体Fe—Mn—Si—Cr形状记忆合金的抗空蚀性能远高于3种应变诱发马氏体相变奥氏体不锈钢和0Cr13Ni5Mo不锈钢.高的局域弹性性质he是Fe—Mn—Si—Cr形状记忆合金具有高抗空蚀性能的主要原因.he是影响亚稳奥氏体金属抗空蚀性能的首要控制因素,空蚀诱发马氏体耗散能量、空蚀表层硬度及加工硬化能力是影响亚稳奥氏体金属抗空蚀性能的第二控制因素.

一种奥氏体不锈钢的空泡腐蚀行为

采用一种新型的奥氏体不锈钢作为耐空泡腐蚀涂层,先表面堆焊,然后进行TIG(钨极惰性气体保护焊)表面重熔改性加工.根据ASTM G32/92标准,空泡腐蚀由超声波振动设备完成.利用X射线衍射仪和扫描电镜(SEM)对试样的空泡腐蚀行为进行了跟踪观察,并对试样的空泡腐蚀率进行了测定.结果表明:在空泡腐蚀过程中,先后发生了相变和马氏体片层的扭曲断裂.空泡冲击能诱发奥氏体到马氏体的相变,并被其吸收;当相变达到饱和点时,马氏体片层开始吸收冲击能,同时逐渐发生扭曲和断裂,最终马氏体片层断裂产生的碎片大量剥落,该材料的空泡腐蚀潜伏期结束.