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作者简介:

林静,女,1995年出生,硕士研究生。主要研究方向为表面改性技术。E-mail:1963436454@qq.com

范其香(通信作者),女,1987年出生,博士,副教授,硕士研究生导师。主要研究方向为表面工程。E-mail:qxfan2015@163.com

中图分类号:TG174;TH161

文献标识码:A

DOI:10.11933/j.issn.1007-9289.20210709001

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目录contents

    摘要

    AlCrTiN 涂层具有优异的综合性能,然而沉积温度对其组织结构与性能的影响还需进一步研究。 采用电弧离子镀和脉冲直流磁控溅射复合沉积技术,改变沉积温度(300 ℃和 400 ℃ )制备两种不同的 AlCrTiN 涂层。 结果表明:两种 AlCrTiN 涂层主要相均为 fcc-(Al,Ti,Cr)N 相,沿(111)晶面择优生长。 沉积温度为 400 ℃ 时,涂层具有更高的硬度和弹性模量,更低的残余应力、摩擦因数和磨损率,表现出更好的力学性能和抗摩擦磨损性能。 两种涂层经过 700 ℃保温 1 h 后,由于涂层内原子扩散和缺陷愈合,硬度和结合力进一步提高。 切削性能测试表明:300 ℃ 和 400 ℃ 温度下制备的涂层铣刀寿命分别为无涂层铣刀的 3. 2 倍和 3. 5 倍。 无涂层铣刀的失效形式以磨粒磨损为主,涂层铣刀的失效形式为磨粒磨损、黏着磨损和氧化磨损。 研究成果对高性能 AlCrTiN 四元涂层的制备、理论研究与工程化应用具有指导意义。

    Abstract

    AlCrTiN coating possesses good comprehensive properties, while the effect of deposition temperature on the microstructure and properties needs to be further investigated. Two different AlCrTiN coatings are prepared by arc ion plating and direct current pulsed magnetron sputtering at 300 ℃ and 400 ℃ . Results show that the main phase of the two AlCrTiN coatings is fcc-(Al,Ti,Cr)N phase, which grows preferentially along the (111) crystal plane. The AlTiCrN coating deposited at 400 ℃ possesses higher hardness, elastic modulus, and lower residual stress, friction factor as well as wear rate indicating it has better mechanical properties and wear resistance. After heat treatment at 700 ℃ for 1 h, the hardness and adhesive strength of the two coatings are enhanced, due to atomic diffusion and defect healing. Cutting tests show that the cutting life of the AlCrTiN coated milling cutter is much higher than that of the uncoated milling cutter. The cutting lives of the AlCrTiN coated cutters prepared at 300 ℃ and 400 ℃ are 3. 2 and 3. 5 times larger than that of the uncoated cutter. The uncoated cutter loses efficacy mainly due to abrasive wear, while the coated cutters fail caused by abrasive, adhesive and oxidation wear. The research results have certain guiding significance for the preparation, theoretical research and application of AlCrTiN quaternary coatings.

  • 0 前言

  • 随着加工制造业的快速发展,难加工材料日益增多。 TiN、CrN等最早应用的二元刀具涂层已经无法满足现代工业化要求。近年来, 含Al涂层如AlCrN、AlTiN等因具有较高的硬度、耐磨性和抗高温氧化性能,引起人们的广泛关注。 AlCrN涂层在高温条件下能够形成致密的Cr2O3 和Al2O3 混合氧化膜,有效阻止O向涂层内部扩散和金属离子向涂层外部扩散,降低氧化速率,广泛应用于高速切削加工刀具表面[1-3]。随着Al含量的增加,涂层的抗高温氧化性能增强,因为Al2O3 的吉布斯自由能比Cr2O3 的吉布斯自由能低[4]。但是,过高的Al含量会使涂层晶体结构发生转变,由单相的fcc-(Al, Cr)N转变为fcc-(Cr,Al)N和hcp-AlN双相结构。同时高温下涂层会发生CrN→Cr2N→Cr相转变,使涂层的红硬性下降。

  • TiAlN涂层具有高的硬度和耐磨性能,同时由于TiN相在高温下具有较高的热稳定性,TiAlN涂层具有很好的红硬性。但是,在高温大气条件下,涂层中Ti元素容易发生氧化生成疏松多孔的TiO2,抗氧化性能较差。为进一步改善涂层的综合性能,同时利用AlCrN和AlTiN优异的抗高温氧化性能和高温热稳定性能, 研究者们尝试制备并研究了AlCrTiN四元涂层的组织结构与性能。 FORSEN等[5]研究了Ti含量对AlCrN三元硬质涂层红硬性能的影响,研究表明掺入Ti元素使立方相结构更加稳定, 可有效抑制软质相hcp-AlN的形成, 使得AlCrN涂层的红硬性得到了显著改善。 XU等[6] 对比研究了TiAlN和TiAlCrN涂层的硬度、红硬性和抗高温氧化性等,发现TiAlCrN涂层的力学性能比TiAlN有明显的提升,可大幅度地提升涂层的服役范围,延长刀具的使用寿命。韩亮等[7]研究了CrN、 TiAlN、CrAlN以及CrTiAlN涂层的摩擦性能,结果显示,四种涂层的摩擦因数逐渐减小,耐磨性能逐渐升高。 CrTiAlN涂层在摩擦磨损试验中表现最为优异,不仅因为四元涂层比三元涂层具有更高的硬度, 而且也因为该涂层中含有Al和Cr元素,减少了Ti元素的含量,因此具有更好的摩擦磨损性能。由此可见,四元CrTiAlN涂层比三元涂层具有更高的红硬性、抗高温氧化性能和抗摩擦磨损性能。

  • 工艺参数对涂层的组织结构与性能具有重要影响。贵宾华等[8]研究了脉冲峰值电流对AlCrTiN涂层组织结构和性能的影响。随脉冲峰值电流的增加,涂层结晶性能得到了改善。郑军等[9] 采用可调控高功率脉冲磁控溅射和脉冲直流磁控溅射复合沉积技术制备了AlCrTiN涂层,并研究了靶功率对其性能的影响。随着Ti靶功率的升高,涂层硬度先增大后下降, 最高值可达28.3GPa。在600℃ 及800℃摩擦条件下,Ti靶功率为3.0kW时制备的涂层抗高温摩擦磨损性能最为优异,其磨损率分别为6.9×10-15 m 3/N·m和14.2×10-15 m 3/N·m。但有关研究沉积温度对AlCrTiN涂层影响的报道较少。因此,本文采用电弧离子镀和脉冲直流磁控溅射复合技术,结合电弧离子镀技术高离化率和脉冲直流磁控溅射技术表面光滑的优点,改变沉积温度(300℃ 和400℃)制备两种AlCrTiN涂层,分析并研究沉积温度对涂层微观组织结构、力学性能、高温热稳定性能、摩擦学行为以及切削性能的影响。

  • 1 试验

  • 1.1 涂层的制备

  • 采用电弧离子镀和脉冲直流磁控溅射复合技术,改变沉积温度(300℃ 和400℃)在单晶Si片、硬质合金片和硬质合金四刃立铣刀表面制备了两种AlCrTiN涂层。靶材选用Al55Ti45 靶 ( ϕ100mm × 27mm)和Al60Cr40 靶(300mm×100mm×4.5mm), 其中AlTi靶连接电弧电源,AlCr靶连接脉冲直流磁控溅射电源,放电脉宽为30 μs,频率为20Hz。依次使用脱脂剂、超纯水和无水酒精对基片进行超声清洗,烘干后放入炉中。采用机械泵和分子泵抽真空,当炉内真空达到6mPa时,打开加热器,设置温度为300℃ 或400℃。当炉内真空度再次达到6.7mPa以下时,通入250mL/min的Ar并调节节流阀使炉内压强保持在1.5Pa。在基片上施加-800V的偏压进行辉光清洗,以此清除基片表面污染物,辉光清洗时间为15min。接通AlTi靶电弧电源,调节电流为60A,同时调节节流阀使炉内压强保持在1Pa, 保持偏压不变, 对基片轰击清洗10min。轰击结束后降低Ar流量至200mL/min,降低偏压至-90V,调节节流阀使炉内工作压强为0.8Pa,沉积AlTi过渡层,时间为2min。随后,降低Ar流量为40mL/min,并通入160mL/min的N2, 保持偏压和工作压强不变,沉积AlTiN过渡层,此过程维持10min。最后,调节N2 流量为125mL/min, Ar流量为25mL/min,保持偏压-90V,接通AlCr靶脉冲直流磁控溅射电源,设置AlCr靶功率为2.2kW, 调节AlTi靶电流为70A,压强维持在0.8Pa,沉积时间为4h。

  • 1.2 组织结构与性能表征

  • 利用X射线衍射仪(XRD,D8Advance,Bruker) 测定涂层中的物相组成, 采用扫描电子显微镜 (SEM,Nanosem430) 观察涂层表面和截面形貌,并使用其附带的能谱仪(EDS,Gensis MT XV60) 分析涂层的成分。

  • 采用SuPro FST150应力仪通过曲率半径法测量涂层中的残余应力。采用纳米压痕仪 ( TTXNHT,CSM)测试涂层的硬度、弹性模量和We值,最大载荷为10mN,保压时间为10s,压入深度为100~140nm,小于涂层厚度的1/10,每个样品测试10次,结果取平均值。采用划痕仪(Revetest test, CSM)测试涂层的膜-基结合力,加载力为1~100N, 划痕长度为3mm,每个样品测试2至3次,结果取平均值;采用摩擦试验机(UMT-TRIBOLAB)在室温下对样品进行摩擦磨损试验,选用直径为6mm的Al2O3 球作为摩擦副,转速为119r/min,载荷2N, 磨痕半径为2mm,摩擦时间为20min。采用白光干涉仪(Bruker Contour GT-K) 观察涂层磨痕形貌,并测量磨损体积。

  • 将两种AlCrTiN涂层装入Al2O3 型坩埚中,放入真空退火炉中加热至700℃,保温1h后随炉冷却。采用XRD(D8Advance,Bruker)分析涂层热处理后的相结构,利用纳米压痕仪和划痕仪测试涂层的力学性能。

  • 采用汉川715D立式加工中心测试无涂层刀具和300℃、400℃温度下制备的AlCrTiN涂层刀具的切削性能。工件材料为H13模具钢,刀具直径为6mm。切削参数如表1所示。试验中, 每切削10min使用热成像仪测量并记录切削温度, 用Kistler三向压电铣削测力仪测试刀具的三向切削力F x,F y,F z。由公式F=Fx2+Fy2+Fz21/2计算切削合力。每切削20min取下刀具,采用超景深显微镜观察刀具后刀面的磨损形貌。当后刀面磨损宽度达到0.2mm或者刀具崩刃时停止切削。采用Quanta400型扫描电镜和能谱仪 ( EDS, EDAX GENESIS XM2)观察和分析刀具磨损区的微观形貌和成分。

  • 表1 切削参数

  • Table1 Cutting parameters

  • 2 结果与讨论

  • 2.1 组织结构与形貌

  • 图1 为在300℃ 和400℃ 温度下制备的AlCrTiN涂层的XRD衍射图谱。从图中可以看出,两种涂层衍射峰均位于fcc-TiN、fcc-CrN和fcc-AlN标准衍射峰位的中间,认为主要相结构是NaCl型的fcc-(Al,Ti,Cr) N固溶体,并沿(111) 晶面择优生长。晶粒通常优先沿总能量(表面能+应变能)最低的晶面生长[10]。在NaCl型FCC结构中,(111) 晶面的应变能最低。涂层生长过程中会产生生长应力和热应力,Cr和Ti固溶于AlN相中,引起晶格畸变,应变能增大。此时应变能在总能量中占主导地位,故为了降低应变能,涂层沿( 111) 晶面择优生长。此外,涂层中也检测到微弱的AlTi2和AlCr衍射峰。

  • 图1 300℃和400℃温度下制备的AlCrTiN涂层的XRD衍射图

  • Fig.1 XRD diffraction patterns of AlCrTiN coatings prepared at 300℃ and 400℃

  • 图2 为在300℃ 和400℃ 温度下制备的AlCrTiN涂层的表面和截面形貌图。两种AlCrTiN涂层表面比较致密,但均出现大颗粒,这是电弧离子镀工艺技术沉积涂层中,靶材表面被激发出微小的熔滴,与气体反应后沉积在涂层表面产生的。随着沉积温度增加,涂层表面的大颗粒尺寸和数量有所减小。两种涂层的元素成分和表面粗糙度如表2所示。 400℃ 温度制备的涂层表面粗糙度略低于300℃温度制备的涂层表面粗糙度,分别56.67nm和5 6.39nm。随着沉积温度升高,涂层中Al原子含量变化不大,而Cr和Ti原子含量略微降低,N原子百分比略微升高。 N原子百分比升高,可能是因为随着沉积温度升高,金属离子或原子与氮反应更充分。

  • 图2 AlCrTiN涂层的表面和截面形貌

  • Fig.2 Surface and cross sectional morphologies of AlCrTiN coatings

  • 表2 两种AlCrTiN涂层的元素成分和表面粗糙度

  • Table2 Element compositions and surface roughness of the two AlCrTiN coatings

  • 从截面形貌图可以看到:两种涂层均表现出细小的柱状晶结构。涂层厚度分别为1.64 μm和1.88 μm。随着沉积温度升高,涂层沉积速率增大, 故厚度增大。这是因为沉积温度升高,离子能量增强[11],沉积到基体表面时粒子的动能增大,数量增多,导致沉积速率加快。

  • 2.2 力学性能

  • 在300℃和400℃温度下制备的AlCrTiN涂层的 HEH/E H 3/E ∗2We 值如表3所示。随着沉积温度由300℃升高至400℃,AlCrTiN涂层硬度和弹性模量由10.58GPa和401.80GPa分别增加至17.23GPa和405.63GPa。这可能是因为沉积温度提高,原子扩散能力增强,涂层更致密,氮化反应更充分,因此硬度大幅度上升。沉积温度为400℃ 时,涂层具有更高的 H/EH 3/E ∗2We 值,说明在该温度下沉积的涂层具有更好的抗弹性变形和抗塑性变形能力[10,12-13]。随着沉积温度升高,涂层的残余压应力由2.04GPa降低到1.03GPa,这是因为沉积温度升高,涂层内部结晶度增强,原子排列更加规则,孔洞减少,内部缺陷密度降低,因此产生的残余压应力下降[14]

  • 图3 为在300℃ 和400℃ 温度下制备的AlCrTiN涂层的声发射信号和划痕形貌。随着加载力增大,涂层中出现微小的裂纹,声信号轻微波动, 此时对应的加载力为L C1。两种涂层的L C1 值分别为29.0N和31.9N。沉积温度为400℃时,涂层具有更大的 L C1 值。 L C1 值越大,涂层抵抗破坏的能力越强,即韧性更好[15]。继续增大加载力,涂层与基体发生剥离,声发射信号急剧增强,此时对应的临界载荷为 L C2。一般以 L C2 作为衡量涂层与基体结合力的标准[16]。 300℃ 和400℃ 温度下制备的AlCrTiN涂层与基体的结合力分别为40.2N和39.4N,较为接近。

  • 表3 两种AlCrTiN涂层的 HEH/E H 3/E2WeσL C1L C2

  • Table3 HEH/E H 3/E2, We, σ and L C1, L C2 values of two AlCrTiN coatings

  • 图3 AlCrTiN涂层声发射信号和划痕形貌图

  • Fig.3 Acoustic emission signal and scratch morphologies of AlCrTiN coatings

  • 2.3 抗摩擦磨损性能

  • 图4 为在300℃和400℃温度下制备的AlCrTiN涂层的摩擦因数曲线图。沉积温度为300℃时,涂层在摩擦初期波动较大,属于不稳定阶段,随着摩擦时间延长,逐渐趋于平稳,摩擦因数在小范围内波动; 而沉积温度为400℃ 时,涂层的摩擦因数曲线更加平稳,曲线波动较小。 300℃ 和400℃ 温度下制备涂层的平均摩擦因数分别为0.630 8和0.585 8。图5显示了两种涂层的磨损率, 分别为1.066 × 10-6 mm 3/N·m和9.59×10-7 mm 3/N·m。涂层的摩擦因数和磨损率都随沉积温度增加而降低, 符合Archard理论[17],即涂层的摩擦因数与硬度成反比。另外,400℃ 温度下制备涂层的 H/EH 3/E ∗2We 值更高,说明其具有更强的抗弹性变形和抗塑性变形能力,摩擦过程中不容易产生裂纹,有利于降低磨损率。

  • 图4 AlCrTiN涂层的摩擦因数曲线图

  • Fig.4 Friction coefficient vs time curves of AlCrTiN coatings

  • 图5 AlCrTiN涂层的磨损率

  • Fig.5 Wear rate of AlCrTiN coatings

  • 图6 为在300℃ 和400℃ 温度下制备的AlCrTiN涂层的磨痕形貌图。由图可知,两种涂层经过载荷循环作用,磨痕均呈现出完整且未被磨穿的状态,表现出良好的耐磨性。沉积温度为400℃ 的涂层磨痕更窄,这是由于其硬度较高,可以有效抵抗对磨副的压入。此外,它具有较高的 H/EH 3/E2 值,更好的韧性和弹性恢复能力,能够将施加在涂层表面的载荷在更宽的区域内得到释放[13,18],高韧性材料在剪切应力作用下更容易产生滑移,从而有效避免犁沟状磨损现象的发生, 提高耐磨性能[19]

  • 图6 AlCrTiN涂层的磨痕形貌图

  • Fig.6 Wear scar morphology of AlCrTiN coatings

  • 2.4 高温热稳定性能

  • 图7 为两种AlCrTiN涂层在700℃ 真空条件下保温1h后的XRD衍射图。从图中可以看到,两种涂层经过热处理后,主要相结构仍为NaCl型的fcc-(Al,Ti,Cr) N,含有少量的AlTi2、AlCr合金相。涂层中fcc-(Al,Ti,Cr)N相依然沿(111)晶面择优生长。与热处理前的衍射峰位相比,fcc-(Al,Ti,Cr)N衍射峰向大角度偏移,这是因为涂层经过700℃ 保温1h后,内部发生应力弛豫和缺陷愈合,使压应力降低[20]

  • 图7 AlCrTiN涂层在700℃保温1h后的XRD衍射图

  • Fig.7 XRD diffraction patterns of AlCrTiN coatings after heat treatment at 700℃ for 1h

  • 图8 为在300℃ 和400℃ 温度下制备的AlCrTiN涂层热处理前后的加载卸载曲线。从图8中可以看出: 在相同载荷作用下, 热处理后的AlCrTiN涂层,最大压入深度均减小。硬度分别由10.58GPa和17.24GPa提升到24.32GPa和25.97GPa。涂层硬度提升是因为真空热处理后,原子发生扩散,缺陷愈合。此外,两种涂层经过700℃ 保温1h后的 H/EH 3/E ∗2We 也有所提高,如表4所示。说明两种涂层热处理后,抗弹性变形、抗塑性变形能力以及韧性增强。

  • 图8 AlCrTiN涂层热处理前后的加载卸载曲线

  • Fig.8 Loading and unloading curves of AlCrTiN coatings before and after heat treatment

  • 表4 两种AlCrTiN涂层热处理后的 HE H/E H 3/E ∗2We

  • Table4 HE H/E H 3/E 2, We value of the two AlCrTiN coatings after heat treatment

  • 图9 为300℃和400℃ 温度下制备的AlCrTiN涂层在700℃真空退火后的临界载荷L C1L C2 值。涂层的结合强度与涂层硬度、弹性模量、We值、表面粗糙度、残余应力、结构致密性和晶体缺陷有关[21]。由图可知,两种AlCrTiN涂层经过700℃ 保温1h热处理后,临界载荷 L C1L C2 均呈现上升趋势。 L C1 值分别由28.97N和31.92N提高至35.69N和37.71N,L C2 值分别由40.2N和39.4N提高至40.6N和42.2N。一方面是因为热处理后涂层硬度提高,有利于结合力增强。另一方面是在加热过程中,涂层内部原子扩散,离子空位等缺陷愈合有助于提高涂层与基体之间的结合力。

  • 图9 两种AlCrTiN涂层热处理后的 L C1L C2

  • Fig.9 L C1 and L C2 values of the two AlCrTiN coatings before and after heat treatment

  • 2.5 切削性能

  • 图10 为无涂层铣刀和AlCrTiN涂层铣刀磨损宽度随时间的变化曲线。由曲线可以发现:无涂层铣刀后刀面平均磨损宽度随着切削时间增加迅速增长,很快达到了磨钝标准。与无涂层铣刀相比,涂层铣刀后刀面磨损速率明显降低。以磨损宽度0.2mm为磨钝标准,无涂层铣刀、300℃ 和400℃ 温度制备的涂层铣刀的切削寿命分别为78min、 249min和270min。 300℃和400℃温度制备的涂层铣刀切削寿命分别是无涂层铣刀的3.2倍和3.5倍。由此可知:AlCrTiN涂层可有效延长刀具的切削寿命,这是因为涂层提高了刀具的硬度和耐磨性。 400℃比300℃温度下制备的涂层铣刀具有更长的切削寿命,这是因为400℃ 制备涂层具有更高的硬度和韧性,同时摩擦因数较低,有利于提高刀具的切削性能。

  • 图11 为无涂层铣刀和两种AlCrTiN涂层铣刀切削温度随时间的变化曲线。从图中可以看出:切削10min时,三把铣刀切削温度相近,均在100℃ 左右;随着切削时间延长,无涂层铣刀切削温度直线上升,磨损剧烈。刀具达到磨钝标准时,切削温度为210.9℃。观察300℃和400℃制备涂层刀具切削温度曲线,可以看出除个别时间点(10min的奇数倍)温度较上个时间点有所降低,这是因为刀具取出,热量散发,温度降低;两把刀具切削温度基本上随着切削时间延长不断增大,切削时结束时,达到最高温度,分别为563.9℃ 和581.3℃。涂层铣刀达到磨钝标准时的温度远高于无涂层铣刀,一方面可能是因为AlCrTiN涂层属于陶瓷材料,其导热系数低,传热慢[22];另一方面是涂层铣刀的切削时间更长,刀具磨损后与工件摩擦加剧,温度不断增加。

  • 图10 无涂层铣刀和两种AlCrTiN涂层铣刀磨损宽度随时间的变化

  • Fig.10 Wear width vs cutting time curves of the uncoated and AlCrTiN coated milling cutters

  • 图11 无涂层铣刀和两种AlCrTiN涂层铣刀切削温度随时间的变化

  • Fig.11 Cutting temperature vs cutting time curves of uncoated and two AlCrTiN coated milling cutters

  • 图12 为无涂层铣刀和两种AlCrTiN涂层铣刀切削力随切削时间的变化曲线。无涂层铣刀在切削前60min以内,切削力不断增大至104.32N,随后切削力波动较大。 300℃和400℃温度制备AlCrTiN涂层铣刀,在切削140min前,切削力均呈稳定上升趋势, 但在140min后两把涂层铣刀切削力也出现较大的波动现象。切削后期切削力波动较大,可能是由于刀具磨损增大,切削过程中振动加剧。

  • 图12 无涂层铣刀和两种AlCrTiN纳涂层铣刀切削力随时间的变化

  • Fig.12 Cutting force vs cutting time curves of the uncoated and two AlCrTiN coated milling cutters

  • 图13 为无涂层铣刀和两种AlCrTiN涂层铣刀切削20min和达到磨钝标准时的磨损形貌。由图13a~13c可知:同样切削20min,两把涂层铣刀的切削宽度大约在0.03mm,而无涂层铣刀的磨损宽度为0.07mm。无涂层铣刀的磨损宽度是涂层铣刀的2.4倍左右,说明涂层铣刀具有更高的耐磨性能。

  • 当三把铣刀都达到磨钝标准时,后刀面磨损形貌如图13d~13f所示,无涂层铣刀后刀面磨损带呈现出一道道清晰的条状沟痕,这些沟痕是因为工件材料中的硬质点与刀具接触,划伤刀具表面,使刀具发生严重的磨粒磨损[23]。在切削过程中,持续伴随着磨粒磨损, 是无涂层刀具失效的主要原因。 300℃下制备的涂层铣刀后刀面不仅呈现出一道道沟痕,表面还存在一些附着物,这些附着物是刀具与工件材料发生粘结形成的积屑瘤,积屑瘤在切削过程中动态生长,在其被切屑带走时,会带走涂层甚至刀具表面材料, 挤压涂层刀具表面, 加速刀具磨损[24-25]。 400℃下制备的涂层铣刀后刀面也有沟痕与积屑瘤,同时出现少量的蓝色物质,通过EDS分析该区域主要成分是O和W元素,说明在高温下刀具中的W和O发生氧化,生成了氧化钨。

  • 图13 无涂层铣刀和两种AlCrTiN涂层铣刀切削20min和达到磨钝标准时的磨损形貌

  • Fig.13 Wear morphologies of the uncoated and two AlCrTiN coated milling cutters

  • 采用扫描电镜进一步观察图13e、13f中标记区域的磨损形貌,如图14所示。由图可知,两种涂层铣刀后刀面均有条状沟痕,这是磨粒磨损造成的。同时刀具表面附着许多块状物,这可能是工件材料粘附于刀具上形成的积屑瘤。采用EDS分析了图14a、14b中A、B和C区域的元素成分。两种涂层A区域均含有大量的O、Fe和Si元素,而Al、Cr、Ti元素含量较少,说明在高速切削下,工件材料发生氧化,生成了Fe、Si的氧化物,附着于刀具表面切削界面处。区域B均检测到了大量的Fe元素,含量为50at.%左右,还检测到12at.%左右的O元素,此外也检测到少量的Mo、V等元素,证明工件材料在切削过程中发生粘结,形成积屑瘤附着在后刀面上。两涂层区域C的EDS结果显示:主要元素为W、Co、C等, 还有微量的Al、 Cr、 Ti元素, 说明切削区AlCrTiN涂层均已被磨损掉,露出基体。综上所述, 无涂层铣刀的磨损机理主要是磨粒磨损,涂层铣刀的失效形式是磨粒磨损、粘着磨损和氧化磨损。

  • 图14 AlCrTiN涂层铣刀后刀面扫描电镜图

  • Fig.14 SEM image of the flank face of AlCrTiN coated milling cutter

  • 3 结论

  • 采用电弧离子镀和磁控溅射复合技术,改变沉积温度制备了两种AlCrTiN四元涂层,研究了沉积温度对涂层组织结构与性能的影响。主要结论如下:

  • (1) 在300℃ 和400℃ 温度下制备的AlCrTiN涂层主要由fcc-(Al,Ti,Cr)N相组成,沿(111)晶面择优生长。随着沉积温度增大,沉积速率增加,涂层厚度增大。

  • (2) 400℃ 比300℃ 温度下制备的AlCrTiN涂层表现出更好的力学性能和耐磨性。在700℃保温1h后,两种涂层的硬度、结合力都有很大提升,表现出优异的高温热稳定性。

  • (3) 针对H13模具钢切削,300℃ 和400℃ 温度下制备的涂层铣刀切削寿命分别是无涂层铣刀的3.2倍和3.5倍。

  • 综上,采用电弧离子镀和磁控溅射复合技术可以制备出性能优异的AlCrTiN涂层,用于模具钢切削显著提升刀具使用寿命,同时有望用于切削其他难加工材料加工。

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