镁合金表面热喷涂WC-10Co-4Cr粒子沉积及分布特性

为了探究高速空气燃料热喷涂(activated combustion-high velocity air fuel,AC-HVAF)过程中喷涂粒子撞击基材后的沉积特性。采用AC-HVAF热喷涂技术在AZ80镁合金基体上沉积WC-10Co-4Cr硬质涂层。通过离散沉积实验获得薄层沉积粒子,探讨各种沉积形貌的种类、形成原因、结合机制及射流中粒子的径向和轴向分布。结果表明:在AC-HVAF粒子沉积过程中,嵌入型沉积为主要的沉积形貌,同时包含少量的破碎型与空腔型沉积粒子。在涂层的形成过程中,嵌入型沉积对涂层/基体结合性能起重要作用;空腔型沉积的小颗粒及破碎型沉积的大颗粒是造成沉积效率下降的主要原因。喷涂粒子主要集中在射流中心,越靠近射流边缘,空腔型沉积粒子越多,最终导致AC-HVAF粒子射流呈现出空间分布特征。

超声速火焰喷涂WC-10Co4Cr涂层对TC11钛合金耐磨性和耐蚀性的影响

采用超声速火焰喷涂(HVOF)工艺,在随钻仪器零件常用材料TC11钛合金表面制备金属陶瓷涂层WC-10Co4Cr,利用冲击试验机测量喷涂前后钛合金的冲击韧性,使用磨粒磨损试验机测定涂层的耐磨性,采用电化学测试分析涂层的耐蚀性。结果表明:HVOF工艺对TC11钛合金的组织和性能影响较小,与未喷涂的钛合金相比,界面处基体的显微组织和显微硬度没有明显变化,冲击韧性稍有提高;HVOF工艺稳定可靠,涂层呈片层结构,致密度高,涂层的孔隙率为2.55%,硬度达到1400 HV,涂层主要由WC和W2C相组成,其与基体结合良好,为机械结合;金属陶瓷涂层能够显著改善钛合金的耐磨性和耐蚀性,喷涂涂层钛合金的磨损量是未喷涂钛合金的1.56%,喷涂涂层钛合金的磨损机制是磨粒磨损,未喷涂涂层钛合金磨损机制是磨粒磨损+黏着磨损。

Effects of cubic carbides and La additions on WC grain morphology,hardness and toughness of WC-Co alloys

Effects of Cr3C2,VC and La2O3 additions on the WC grain morphology,hardness and toughness of WC-10Co alloys were investigated.To intensify the grain growth driving force,nano W and nano C,instead of the conventionally used WC,were used as the starting materials.To obtain a three-dimensional WC grain morphology,the natural sinter skins of the alloys were observed directly by scanning electron microscopy.It is shown that the additions have a strong ability in regulating the WC grain morphological and grain size distribution characteristics and the combinations of hardness and toughness.Due to the formation of regular and homogeneous triangular platelet WC grains,WC-10Co-0.6Cr3C2-0.06La2O3 alloy shows an excellent combination of hardness and toughness.The morphological regulation mechanism,the relationship between the WC grain morphology and the properties were discussed.

WC–xVC复合粉的制备及高含量VC对WC–Co基硬质合金微观结构和力学性能的影响

采用两步碳热还原法合成了WC–xVC复合粉,并以此为原料通过真空烧结法制备了不同Co含量(6%和10%,质量分数)的WC–Co–VC硬质合金,研究了烧结温度(1420℃、1440℃和1460℃)对硬质合金致密化过程的影响,分析了Co和VC含量对WC晶粒尺寸以及硬质合金维氏硬度和断裂韧性的影响。结果表明,随着烧结温度的升高,合金的相对密度增大,当烧结温度为1460℃时,所有合金试样的相对密度均大于98.5%。此外,随着VC含量的增加,WC的平均晶粒尺寸减小,这导致样品的硬度提高,断裂韧性降低。当VC质量分数为6%时,WC–6Co硬质合金和WC–10Co硬质合金的硬度均达到最大值,分别为HV301941和HV301838。在烧结温度和VC含量一定的情况下,试样的断裂韧性随着Co含量的增加而增加,试样的硬度随着Co含量的增加而减小。

Effect of pre-deformation on precipitation behavior of AZ80 alloy:Comparison of slip-and twinning-dominant deformation

This study investigates the effect of the deformation mode on the precipitation behavior of an extruded Mg-8.0Al-0.5Zn-0.2Mn(AZ80)alloy.The alloy samples are compared after the application of 3.5%tension and 3.5%compression along the extrusion direction to induce slip-dominant and twinning-dominant deformation modes,respectively.The pre-compressed(PC)sample,which contained numerous{10-12}tension twins,has a reduced grain size and a higher internal strain than the pre-tensioned(PT)sample,which is attributed to the inherent internal strain that occurs during the formation and growth of the twins.As a result,the precipitation behavior of the PC sample is accelerated,leading to its short peak aging time of 32 h,which is lower than those of the PT and as-extruded samples(48 and 100 h,respectively).Furthermore,fine continuous precipitates(CPs)rapidly form within the{10-12}twins,contributing to the enhanced hardness.Discontinuous precipitates(DPs),which have a hardness comparable to the CP-containing twinned regions,in the PC sample experience less coarsening during aging than those in the PT sample due to growth inhibition by the{10-12}twins.Ultimately,the{10-12}twins generated under the twinning-dominant deformation condition lead to enhanced precipitation behaviors,including the preferential formation and refinement of CPs and the suppressed coarsening of DPs.Consequently,pre-deformation that occurs{10-12}twinning exhibits more pronounced effects on precipitation acceleration and microstructural modification than slip-inducing pre-deformation.

WC-10Co4Cr涂层的制备工艺及性能研究

WC-10Co4Cr涂层具有高硬度和良好耐磨损性能,在航空领域应用广泛。采用超音速火焰喷涂法在A100钢表面制备了WC-10Co4Cr涂层,通过正交实验法确定最佳制备工艺,在最佳工艺条件下制备WC-10Co4Cr涂层,测试了涂层的显微硬度、残余应力、结合强度和摩擦系数。结果表明,最佳工艺条件是煤油流量为5.8 SCFH,氧气流量为1900 SCFH,喷涂距离为350 mm,送粉速率为9.5 r/min。在最佳工艺条件下制备的WC-10Co4Cr涂层平均显微维氏硬度为1137,硬度明显高于A100合金钢基底,残余应力造成的弧高值为0.373 mm,涂层的结合强度高于70.9 MPa。制备的WC-10Co4Cr涂层在显微硬度、残余应力和结合强度方面均能达到航空行业标准。WC-10Co4Cr涂层的磨损深度和磨损体积明显低于A100合金钢基底,具有更高的耐磨损性能。A100合金钢的磨损机制为黏着磨损,WC-10Co4Cr涂层的磨损机制为磨粒磨损。

FeCoCrNiMn-WC高熵合金熔覆涂层组织与性能研究

为了探究WC颗粒对熔覆涂层组织与性能的影响,采用1 200 W激光功率和6 mm/s的扫描速度在NM450钢表面制备FeCoCrNiMn-x WC高熵合金熔覆涂层。通过X射线衍射仪(XRD)、扫描电镜(SEM)、维氏显微硬度计、摩擦磨损试验机对涂层的物相、显微组织、力学性能及耐磨性能进行了研究。结果表明:当FeCoCrNiMn高熵合金涂层加入WC颗粒后,高熵合金复合涂层组织主要为FCC和BCC相,含有少量WC、W2C和Cr7C3相,显微结构为柱状晶和胞状晶组织。在10%WC复合涂层综合性能最佳,显微硬度达到最大值484.5 HV0.3;摩擦因数为0.58,磨损量和磨损率最低分别为0.011 4 g与0.857×10^(-5)g/(N·m),复合涂层的磨损方式主要为磨粒磨损与氧化磨损,并伴随黏着磨损。

The Effects of WC on the Microstructures and Wear Resistance of FeCoCrNiB_(0.2) High Entropy Alloy

To improve the wear resistance of the FeCoCrNiB_(0.2)high entropy alloy(HEA),the FeCoCrNiB_(0.2)(WC_(0))and FeCoCrNiB_(0.2)+20wt%WC(WC_(20))HEA coatings were prepared on Q235 steel by laser cladding(LC).The microstructure,hardness,and tribometer of the HEA coatings were investigated using scanning electron microscopy with spectroscopy(SEM/EDS),X-ray diffraction(XRD),vickers microhardness tester,and pin-on-disc tribometer,respectively.The experimental results show that the WC0HEA coating comprises a simple BCC phase mixed with an M_(2)B phase.Adding 20wt%WC,the WC_(20)HEA coating is composed of a simple BCC phase mixed with the Cr_(23)C_(6)carbide phase.The microstructure of the WC_(20)HEA coating is simple,which consists of equiaxed grain and dendritic.The microhardness also increases from 625.5HV to 806.0HV,and the wear mass loss correspondingly decreases from 30.9 to 14.9 mg.W and C atoms formed by WC dissolution are mainly dissolved in the BCC phase,which leads to the solution strengthening effect.Besides,Cr_(23)C_(6)carbides inhibit the growth of the grains,play the role of fine-grain strengthening,and further improve the hardness and wear resistance of the HEA coating.

激光表面重熔对CoCrFeNiW_(0.5)高熵合金组织及性能的影响

采用真空氩弧熔炼制备了非等原子比CoCrFeNiW_(0.5)高熵合金并进行了激光表面重熔处理,系统研究了激光表面重熔对合金相组成、显微组织、硬度及摩擦磨损性能的影响。结果表明:铸态高熵合金的显微组织由枝晶FCC相及枝晶间(FCC+μ)共晶组织组成,激光重熔后合金的共晶组织消失并且晶粒明显细化,金属间化合物μ相以颗粒状分布在等轴FCC的晶界上。与铸态合金相比,激光重熔后合金的硬度提升约17%,与Si_(3)N_(4)陶瓷配副时的摩擦系数降低约7%,磨损率降低约75%,这主要归因于激光重熔过程引起的细晶强化、固溶强化,以及合金组织成分均匀性的提升。

WC-Ni基硬质合金微观结构和物理力学性能调控研究进展

WC-Ni基硬质合金用作磁性材料成形模具、核主泵机械密封关键部件以及磨蚀性服役工况耐磨零件独具优势。由于材料体系的本征特性,与WC-Co合金相比,在黏结金属含量相同和合金晶粒度相近条件下,WC-Ni基合金强度、硬度和韧性均明显较低,高性能化面临挑战。本文对WC-Ni三元合金和含其它合金组元WC-Ni基合金的微观结构和物理力学性能调控,以及含Ti板状晶WC-Ni基合金的研究进展进行综述,旨在奠定高性能WC-Ni基硬质合金新材料高效开发的基础。

CoCrFeNiW_(x)高熵合金黏结剂对WC硬质合金显微组织和力学性能的影响

采用机械合金化方法制备CoCrFeNiW_(x)(x取0.2,0.5,物质的量分数/%)高熵合金粉末,作为黏结剂(添加质量分数分别为6%,10%,14%)与WC粉混合,经放电等离子烧结得到WC硬质合金,研究了高熵合金黏结剂对硬质合金显微组织和力学性能的影响。结果表明:CoCrFeNiW_(x)高熵合金黏结剂具有面心立方和体心立方双相结构,可细化WC硬质合金晶粒;随着高熵合金黏结剂含量的增加,WC硬质合金的维氏硬度降低,断裂韧度和抗弯强度总体呈上升趋势。添加质量分数10%CoCrFeNiW_(0.2)高熵合金黏结剂制备的WC硬质合金综合性能最佳,维氏硬度为1785 HV,断裂韧度为10.6 MPa·m^(1/2),抗弯强度为1373 MPa。

等离子熔覆Fe基/WC-10Co-4Cr涂层的组织与性能研究

目的制备高强度和高硬度的耐磨性涂层,用于已磨损的机械零件表面,以延长其使用寿命,避免机器因磨损而带来的各种故障。方法采用等离子熔覆技术在40CrMnMo表面制备WC-10Co-4Cr/Fe300合金复合熔覆层,研究不同质量分数WC-10Co-4Cr对熔覆层组织和性能的影响。利用金相显微镜、超景深光学显微镜、SEM、EDS、XRD对熔覆层的组织形貌进行表征和物相分析,借助数显显微硬度计和销盘式摩擦磨损试验机测试熔覆层的硬度和耐磨性。结果WC-10Co-4Cr/Fe300合金作为一种复合材料,与基材形成了冶金结合,结合区域无孔洞和裂纹。熔覆层微观结构随着WC-10Co-4Cr含量的增加,逐渐由柱状晶向树枝晶过渡,它主要由Fe6W6C、(Cr、Fe)23C6和WC相组成。熔覆层的平均硬度大致随着WC-10Co-4Cr含量的增加而提高,当WC-10Co-4Cr的质量分数达到20%时,熔覆层的硬度最高(518.5HV0.2),大约是基体硬度的1.7倍。熔覆层的主要摩擦机理为磨粒磨损,随着WC-10Co-4Cr含量的增加,熔覆层的耐磨性得到显著改善。当WC-10Co-4Cr的质量分数为30%时,其磨损量比基体的总磨损量少0.0186 g,熔覆层的耐磨性最好。结论加入的WC-10Co-4Cr粉末与Fe300合金粉末反应生成了Fe6W6C、(Cr、Fe)23C6强化相,显著提高了熔覆层的硬度和耐磨性。

激光能量密度对65Mn钢表面Ni60A/WC复合涂层摩擦磨损性能的影响规律

目的改善旋耕刀65Mn钢的摩擦磨损性能,提高农机触土零部件的使用寿命。方法采用激光熔覆技术在65Mn钢基体表面制备Ni60A/WC复合涂层。通过改变激光功率调节激光能量密度,在不同能量密度下制备Ni60A/WC复合涂层,观察并测试不同参数下复合涂层试样的宏观形貌、微观结构、物相组成、元素分布、显微硬度及摩擦磨损特性,研究激光能量密度对Ni60A/WC复合涂层组织演变及摩擦磨损性能的影响规律和机理。结果Ni60A/WC复合熔覆层顶部主要有胞状晶和树枝晶,分布较紧密,熔覆层中部主要有树枝状晶,熔覆层底部主要为胞状晶和垂直交界面生长的枝晶,且分布均匀致密。随着激光能量密度的升高,熔覆层的熔高和熔深增加显著,WC硬质相颗粒发生分解,硬质相的数量明显减少,涂层的平均显微硬度降低。在激光能量密度为120 J/mm^(2)时,熔覆层的平均显微硬度为587.1HV1.0,相较于基体,提升了约1.8倍。此时熔覆层的平均摩擦因数最小,为0.312,相较于基体,得到显著提升,摩擦磨损机制为轻微的磨粒磨损。经田间试验测试发现,在激光能量密度为120 J/mm^(2)时制备的带有熔覆层的旋耕刀相较于无熔覆层的旋耕刀,其磨损质量降低了63%。结论通过控制激光能量密度,可以有效调控Ni60A/WC熔覆层的硬度和耐磨性,可为农机触土易磨损件的减摩耐磨表面强化改性提供理论指导。

Wear resistance performance of high entropy alloy–ceramic coating composites synthesized via a novel combined process

Titanium nitride(TiN), characterized by its high hardness and strength, was widely used as ceramic coating to improve the wear resistance of matrix materials. In this work, AlCrFeNiTi_(x) high-entropy alloy(HEA) powders were synthesized by direct electrochemical reduction in molten salt from the mixed metal oxides. Then,TiN ceramic coating on the AlCrFeNiTi_x bulk HEA containing the topologically close-packed(TCP) phase(σphase, Laves phase, and Ti_(3)Al phase) was prepared by vacuum hot pressing sintering, where nitride element come from boron nitride parting agent sprayed on the graphite mold. The effect of titanium content on the crystal structure, microstructure, hardness, and wear resistance of the products were investigated by X-ray diffraction, field emission scanning electron microscope, field emission electron-probe microanalysis,Vickers hardness tester, and friction–abrasion testing machine. The bulk HEAs exhibit excellent hardness and its hardness increases significantly with the increase of titanium content. The wear mechanism changes from both of predominantly delamination and accompanied oxidative wear to single delamination wear,which is due to ultra-high melting point and high hot hardness of TiN, that can effectively prevent the oxidation and deformation of the worn surface. Formation of the ceramic coatings containing the TiN second phase and TCP phase are the key factor to AlCrFeNiTi_x alloy with the excellent hardness and wear properties.

Influence of quenching medium on the dendrite morphology,hardness,and tribological behaviour of cast Cu-Ni-Sn spinodal alloy for defence application

Cu-Ni-Sn spinodal alloys(Spinodal bronze)are potential materials with robust applications in components associated with defence applications like bearings,propellers,bushes,and shafts of heavily loaded aircraft,off-road vehicles,and warships.This paper presents a comparative study using water,Brine solution,and SAE 40 oil as the quenching media in regular bronze(Cu-6Sn)and spinodal bronze(Cu-9Ni-6Sn)alloys.Morphological analysis was conducted by optical microscopy,transmission electron microscopy(TEM),and X-ray diffraction technique(XRD)on bronze and spinodal bronze samples immersed in the three different quenching media to understand the grain size and hardness values better.Tribological analysis was performed to analyze the effect of quenching media on the wear aspects of bronze and spinodal bronze samples.The hardness value of the brine-aged spinodal bronze samples was as high as 320 Hv,and the grain size was very low in the range of 60μm.A quantitative comparison between brine-aged regular bronze and brine-aged spinodal bronze showed that the hardness(Hv)was almost 80%higher for brine-aged spinodal bronze.Further,the grain size was approximately 30%finer for spinodal bronze when compared with regular bronze.When the load was increased in spinodal bronze samples,there was an initial dip in wear rate followed by a marginal increase.There was a steady increase in friction coefficient with a rise in load for brine-aged regular bronze and spinodal bronze samples.These results indicate that brine solution is the most effective quenching medium for cast Cu-Ni-Sn spinodal alloys.

冷喷涂Ti/WC复合涂层的组织与耐磨性研究

为解决钛及其合金磨损性能较差的问题,采用高压冷喷涂技术在Ti6Al4V合金基体上沉积了2种不同成分的Ti/WC复合涂层,通过室温下的干滑动摩擦磨损试验分别测试了基体与复合涂层的摩擦性能,并采用扫描电镜及拉曼光谱对磨损表面进行了观察与表征。结果表明,与Ti6Al4V基体的磨损率(4.06×10-7 mm3/(N·m))相比,复合涂层的磨损率降低了一个数量级,表现出优异的耐磨性。此外,涂层内WC含量的增加,提高了涂层的显微硬度,涂层的耐磨性也随之提升。在磨损轨迹表面,由TiO2、WO3以及WC碎片构成的摩擦膜能够有效避免磨球与涂层表面的直接接触,从而降低磨损程度。因此,冷喷涂Ti/WC复合涂层在钛合金磨损防护方面具有一定的应用前景。

激光熔覆Ni/WC梯度复合涂层的组织与性能研究

目的减少涂层内部缺陷,提高Cr12MoV模具钢表面的显微硬度及耐磨性。方法采用激光熔覆技术在Cr12MoV钢上逐层制备Ni60-Ni60/25%WC(Ni/WC)梯度复合涂层。借助X射线衍射仪(XRD)、扫描电子显微镜(SEM)、能谱仪(EDS)、显微硬度计、摩擦试验机和冲击试验机,研究梯度复合涂层的物相组成、微观组织、显微硬度、耐磨性与冲击韧性。结果在Cr12MoV的基体上制备Ni/WC梯度复合涂层,Ni60层与Ni60/25%WC冶金结合理想。Ni/WC梯度复合涂层的表面主要物相为γ-(Fe,Ni)、FeNi_(3)、CrB、Cr_(7)C_(3)、Cr_(23)C_(6),从Ni60层底部到顶部依次为胞状晶、柱状晶、细小的等轴枝晶。Ni/WC梯度复合涂层硬度呈梯度分布,涂层的平均硬度达到698.5HV,相较于基体提高了约55.2%。与基体相比,Ni/WC梯度复合涂层表现出更好的耐磨性能,摩擦系数和磨损率分别下降了40.92%和28.6%,其中基体表现为黏着磨损,然而涂层整体表现为磨粒磨损。但较基体而言,Ni/WC梯度复合涂层的冲击韧性值降低了32.48%,复合涂层区域表现为脆性断裂。结论Ni/WC梯度复合涂层冶金结合良好,同时与基体相比,Ni/WC梯度复合涂层可以有效提高硬度及耐磨性,但冲击韧性有所降低。

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.

FeCoCrNiAl高熵合金涂层的等离子熔覆工艺研究

采用等离子熔覆技术在45号钢基体表面制备FeCoCrNiAl高熵合金涂层,研究熔覆电流和离子气流量对涂层表面形貌及孔隙率的影响。结果表明,当熔覆电流为180 A、离子气流量为2.5 L/min、熔覆速度为100 cm/min时,制备出的FeCoCrNiAl合金涂层与基体结合良好、无裂纹,孔隙率达到最低值0.0276%。该工艺制备的FeCoCrNiAl合金涂层高熵效应显著,但组织中除了具有BCC结构相以外,还存在具有FCC结构的Fe-Cr相、Ni-Co相、富Ni相、富Al相等成分。FeCoCrNiAl高熵合金涂层的显微硬度为500 HV,达到45钢基体的2倍以上。

Application of response surface methodology to maximize tensile strength and minimize interface hardness of friction welded dissimilar joints of austenitic stainless steel and copper alloy

An attempt was made to optimize friction welding parameters to attain a minimum hardness at the interface and a maximum tensile strength of the dissimilar joints of AISI 304 austenitic stainless steel （ASS） and copper （Cu） alloy using response surface methodology （RSM）. Three-factor, five-level central composite design matrix was used to specify experimental conditions. Twenty joints were fabricated using ASS and Cu alloy. Tensile strength and interface hardness were measured experimentally. Analysis of variance （ANOVA） method was used to find out significant main and interaction parameters and empirical relationships were developed using regression analysis. The friction welding parameters were optimized by constructing response graphs and contour plots using design expert software. The developed empirical relationships can be effectively used to predict tensile strength and interface hardness of friction welded ASS-Cu joints at 95% confidence level. The developed contour plots can be used to attain required level of optimum conditions to join ASS-Cu alloy by friction welding process.