郝建軍，占志國，侯俊英,2，趙建國，劉敬春,2，殷常峰

·農(nóng)業(yè)裝備工程與機械化·

旋耕刀Fe/WC/CeO2等離子堆焊層制備及其組織性能

郝建軍1,2,3，占志國1，侯俊英1,2，趙建國1,2,3，劉敬春1,2，殷常峰4

（1. 河北農(nóng)業(yè)大學機電工程學院，保定 071001；2. 河北省智慧農(nóng)業(yè)裝備技術(shù)創(chuàng)新中心，保定 071001；3. 河北省農(nóng)業(yè)機械作業(yè)刀具重點實驗室，定州 073000；4. 山東旭拓新材料科技有限公司，濰坊 261000）

針對農(nóng)業(yè)觸土部件因耐磨性能差、沖擊韌性低而導致刀具壽命短、失效頻繁等問題，采用等離子堆焊技術(shù)在Q235鋼基材上成功制備了Fe/WC/CeO2金屬陶瓷復合涂層，分析了CeO2對Fe/WC/CeO2金屬陶瓷復合涂層性能的影響及其對涂層的作用機理。以堆焊電流、堆焊速度、送粉速率、堆焊距離為試驗因素，磨損量為評價指標，通過正交試驗優(yōu)化了Fe/WC/CeO2等離子堆焊層制備工藝參數(shù)：堆焊電流50 A，堆焊距離5 mm，堆焊速度15 cm/min，送粉速率25 g/min。利用掃描電子顯微鏡、X射線衍射儀、能譜儀分析了堆焊層顯微組織、物相組成，采用維氏顯微硬度計、摩擦磨損試驗機、沖擊試驗機、土槽試驗臺等測試了堆焊層顯微硬度、耐磨性和沖擊韌性，利用電化學工作站分析了堆焊層的耐蝕性。結(jié)果表明，堆焊層與基體呈良好的冶金結(jié)合，涂層主要有魚骨狀、長桿狀、球狀、六方形狀等組織構(gòu)成，堆焊層主要由γ-Fe、Fe-Cr-Ni固溶體、WC、M7C3、Cr7C3、Cr23C6、W2C等物相組成。與Fe/WC堆焊層相比，F(xiàn)e/WC/CeO2堆焊層平均顯微硬度提高22%，沖擊韌性提高29%。土槽試驗與田間試驗表明，與65Mn旋耕刀相比，F(xiàn)e/WC/CeO2堆焊層旋耕刀的磨損量分別降低71%和65%；與Fe/WC堆焊層旋耕刀相比，F(xiàn)e/WC/CeO2堆焊層旋耕刀的磨損量分別降低17%和15%。Fe/WC/CeO2堆焊層具有較好的耐磨、耐蝕和耐沖擊綜合性能，研究結(jié)果可為犁鏵、深松鏟等農(nóng)業(yè)觸土部件強化提供參考。

顯微結(jié)構(gòu)；性能；等離子堆焊；堆焊層；旋耕刀

0 引 言

中國農(nóng)業(yè)機械化的快速發(fā)展，對農(nóng)機裝備關鍵部件的綜合性能及使用壽命要求也越來越高[1-2]。農(nóng)業(yè)機械是實現(xiàn)農(nóng)業(yè)機械化的基本物質(zhì)保證，是現(xiàn)代農(nóng)業(yè)的有力支撐。耕整地機械作為農(nóng)業(yè)機械化的首要和基礎環(huán)節(jié)，對于提高耕地產(chǎn)能、保障糧食安全，具有十分重要的意義。農(nóng)業(yè)觸土部件長期承受土壤中砂石、作物秸稈等的摩擦極易發(fā)生磨損失效，嚴重影響了農(nóng)業(yè)機械的使用壽命和工作可靠性[3-6]。改善農(nóng)業(yè)機械觸土部件的耐磨性，延長其使用壽命，是加快農(nóng)業(yè)機械化及農(nóng)機裝備產(chǎn)業(yè)轉(zhuǎn)型升級亟待解決的問題之一。

為提高農(nóng)業(yè)觸土部件的使用壽命，張旭等[7]采用氧乙炔火焰噴焊在滅茬刀上制備了耐磨性優(yōu)異的Fe6涂層。郝建軍等[8]采用等離子堆焊技術(shù)在旋耕刀上制備了較65Mn旋耕刀平均磨損量減小50%的Fe-Cr-C-V復合涂層。趙建國等[9]采用火焰噴焊技術(shù)在深松鏟尖制備鐵基合金涂層，并利用噴焊余溫進行淬火處理，結(jié)果表明涂層深松鏟尖耐磨性明顯提高。張校珩[10]利用等離子堆焊在割草刀上制備了Fe基合金堆焊層，并對其進行微波熱處理，結(jié)果表明割草刀耐磨性和使用壽命明顯提高。上述方法制備的涂層均在不同程度上提高了農(nóng)機觸土部件的耐磨性，延長了使用壽命，但上述涂層大多存在韌性低、易發(fā)生脆斷等不足，難以滿足旋耕機大型化、復式化、高速化發(fā)展需求。

稀土改性是改善涂層性能的常用手段，它能有效消除涂層材料分布不均及晶粒粗大，使涂層具有硬度高、強度高、韌性高、耐蝕性好等優(yōu)異性能[11-12]。趙運才等[13]以稀土氧化物CeO2為添加劑，利用等離子噴涂技術(shù)在45鋼表面制備了Ti-Al/WC金屬陶瓷復合涂層，結(jié)果表明，CeO2的加入使涂層內(nèi)部晶粒得到細化，顆粒物含量大幅度減少，孔洞變小，裂紋數(shù)量顯著降低。Chen等[14]以稀土氧化物CeO2為添加劑，采用激光熔覆制備了Fe基合金涂層，分析表明CeO2可減少涂層裂紋傾向和孔隙率，顯著提高涂層與基體的結(jié)合強度。本文采用等離子堆焊制備Fe/WC/CeO2堆焊層，分析CeO2稀土氧化物對涂層性能的影響，以期為深松鏟、犁鏵、割草刀等農(nóng)業(yè)觸土部件表面強化提供參考。

1 堆焊層制備

1.1 試驗材料

基體為100 mm×40 mm×10 mm的Q235鋼，堆焊粉末為上海鑄宇材料科技有限公司生產(chǎn)的純度99.5%，粒度分別為48～100m與45～100m的FJ-19和NiWC粉末，化學成分組成見表1。純度為99.99%，粒度為15～20m的CeO2粉由中諾新材（北京）科技有限公司生產(chǎn)。

表1 堆焊粉末化學成分及質(zhì)量分數(shù)

混合粉末中CeO2含量對涂層組織和性能具有顯著影響。CeO2含量太小，堆焊層硬度與耐磨性提升效果不明顯，而CeO2含量過高，則會降低堆焊過程中熔池液態(tài)金屬的流動性，導致堆焊層成分偏析嚴重、應力集中加劇、組織缺陷增多、耐磨性降低[14]。本研究前期試驗表明，等離子堆焊制備Fe/WC/CeO2時，CeO2質(zhì)量分數(shù)為3%時，CeO2對改善Fe/WC堆焊層耐磨性能效果明顯（如圖1）。

參考相關文獻[15-16]并結(jié)合前期預試驗結(jié)果，本研究試驗用堆焊粉末分別按70%FJ-19+30%NiWC、67%FJ-19+ 30%NiWC+3%CeO2配制?；旌戏勰┓謩e用QM-3SP2型行星式球磨機球磨混合。球磨工藝參數(shù)：轉(zhuǎn)速200 r/min，球磨時間8 h，球料比7∶1，磨球材質(zhì)氧化鋯。

1.2 設備及工藝參數(shù)選取

采用GP-1噴砂機對Q235試件的100 mm×40 mm任一面進行噴砂處理，噴砂工藝參數(shù)為：噴砂壓力0.7 MPa，G16鋼砂，噴砂角75°，噴砂距離100 mm。噴砂完畢后用丙酮溶液清洗以去除試件表面的雜質(zhì)與油污，清洗完畢后用冷風吹干，待用。

等離子堆焊工藝參數(shù)中，堆焊電流、堆焊速度、送粉速率、堆焊距離是影響堆焊層質(zhì)量的主要因素[17-18]。工藝參數(shù)選取不當均會導致堆焊粉末熔化不良或過度熔化，堆焊層成型差，堆焊層耐磨性能變差。

采用DML-V02BD等離子堆焊機（離子氣1.5 L/min，送粉氣2.5 L/min，保護氣0.5 L/min，堆焊角度90°±5°）在經(jīng)表面預處理后的2組基體試件表面分別制備Fe/WC、Fe/WC/CeO2等離子堆焊層。采用HSR-2M型往復式摩擦磨損試驗機測試堆焊層耐磨性，利用FA2204B型電子分析天平稱量磨損量（每組試樣重復3次，結(jié)果取平均值）。以堆焊電流、堆焊速度、送粉速率、堆焊距離為試驗因素，堆焊層磨損量為評價指標，采用四因素三水平L27（34）正交試驗優(yōu)化堆焊工藝參數(shù)。根據(jù)經(jīng)驗[19-22]和設備允許范圍，試驗因素與水平設計見表2。

表2 試驗因素與水平

1.3 優(yōu)化結(jié)果

正交試驗結(jié)果及極差分析見表3，方差分析見表4。

表3 正交試驗結(jié)果及極差分析

表4 方差分析

注：<0.01（極顯著）；0.01<<0.05（顯著）；>0.05（不顯著）。

Note:<0.01 (very significance), 0.01<<0.05 (significance)>0.05 (no significance).

由表3可知，各因素對堆焊層磨損量的影響主次排序均為：堆焊電流、堆焊距離、堆焊速度、送粉速率。由表4可知，堆焊電流、堆焊速度、送粉速率、堆焊距離對堆焊層的磨損量影響顯著。獲得磨損量最小的堆焊層最優(yōu)工藝參數(shù)組合為：堆焊電流50 A，堆焊距離5 mm，堆焊速度15 cm/min，送粉速率25 g/min。采用DML-V02BD等離子堆焊機以上述最優(yōu)工藝參數(shù)制備Fe/WC、Fe/WC/CeO2堆焊層，并對堆焊層組織與性能進行分析。

2 堆焊層組織

2.1 堆焊層顯微組織

圖2為堆焊層掃描電鏡（Scanning Electron Microscope，SEM）形貌。由圖2a、2b可以看出，堆焊層成型較好，無明顯氣孔、裂紋等缺陷，堆焊層與基體結(jié)合區(qū)界面明顯，說明堆焊層與基體相互滲透形成了良好的冶金結(jié)合。與Fe/WC堆焊層相比，F(xiàn)e/WC/CeO2堆焊層結(jié)合區(qū)部位出現(xiàn)了WC顆粒，說明CeO2的凈化作用可使WC等硬質(zhì)顆粒移向堆焊層邊緣，提高堆焊層結(jié)合部的硬度。

由圖2c、2d可知，F(xiàn)e/WC堆焊層中硬質(zhì)相主要呈魚骨狀、長桿狀、球狀，硬質(zhì)相尺寸粗大（長桿狀硬質(zhì)相可達200m）且分布雜亂；與Fe/WC堆焊層相比，F(xiàn)e/WC/CeO2堆焊層中長桿狀硬質(zhì)相尺寸明顯減?。ǔ叽缂s100m）且呈彌散分布，硬質(zhì)相呈魚骨狀、長桿狀、球狀、六方形狀。稀土氧化物CeO2不僅可使熔池中的WC等未熔顆粒移向堆焊層邊緣，同時，還可細化晶粒、凈化晶界，二者的共同作用使得堆焊層中硬質(zhì)相細小且彌散分布。

2.2 堆焊層物相

圖3為堆焊層X射線衍射圖（X-Ray Diffraction, XRD）。由圖3可見，F(xiàn)e/WC堆焊層主要由γ-Fe、Fe-Cr-Ni固溶體及WC、M7C3、Cr7C3、Cr23C6等碳化物硬質(zhì)相組成。與Fe/WC相比，F(xiàn)e/WC/CeO2堆焊層中的碳化物與固溶體峰值有所增加，說明CeO2有助于碳化物增加和固溶體析出。另外，F(xiàn)e/WC/CeO2堆焊層中出現(xiàn)了W2C硬質(zhì)相，這是由于CeO2的使堆焊層中WC硬質(zhì)相脫碳，分解形成W2C。與標準PDF（Powder Diffraction File）卡片比對發(fā)現(xiàn)Fe/WC/CeO2堆焊層的物相衍射峰有較弱偏移，這是由于等離子堆焊快速凝固導致的固溶擴展和熱收縮產(chǎn)生的拉應變畸變[23-25]致使衍射峰發(fā)生了偏移。

因CeO2添加量較少，在Fe/WC/CeO2堆焊層XRD中未發(fā)現(xiàn)CeO2衍射峰。為進一步分析CeO2對涂層組織的影響，采用EDS分析Fe/WC/CeO2堆焊層中元素分布（如圖4）。由圖4可以看出，塊狀物質(zhì)W元素含量較高，可能為未熔的WC顆粒。Ni、W、Ce元素均勻，說明CeO2的添加可使堆焊層中各組織呈彌散分布。

3 堆焊層性能

3.1 堆焊層顯微硬度

利用MH-6維氏顯微硬度儀測試Fe/WC、Fe/WC/CeO2試件截面顯微硬度。測試時，試驗載荷0.5 kg，加載時間15 s，每組試樣重復3次，結(jié)果取平均值。圖5為試件截面顯微硬度圖。

由圖5可知，F(xiàn)e/WC、Fe/WC/CeO2堆焊層顯微硬度分布較均勻，硬度自涂層至基體方向逐漸降低，F(xiàn)e/WC/CeO2堆焊層平均顯微硬度（HV0.5870）較Fe/WC堆焊層顯微硬度（HV0.5710）提高了22%。CeO2使堆焊層WC增強相和Cr23C6、M7C3等硬質(zhì)相的分布更加均勻，從而提高了堆焊層的顯微硬度。與本課題組前期制備的Fe-Cr-C-V堆焊層（HV0.5810）[8]相比，F(xiàn)e/WC/CeO2堆焊層硬度提高了7%。

3.2 堆焊層耐磨性

利用HSR-2M型往復式摩擦磨損試驗機，測試Fe/WC、Fe/WC/CeO2堆焊層磨損量及摩擦系數(shù)。磨損量測試時，加載載荷50 N，往復距離4 mm，磨球為直徑6 mm的Si3N4陶瓷球，試驗時間5 h，試驗中每隔1 h利用FA2204B型電子天平（精度為0.1 mg）稱量一次磨損量，每個試樣重復3次，結(jié)果取平均值；摩擦系數(shù)測試時間60 min，其他測試參數(shù)與磨損量測試相同。

3.2.1 磨損量

試件磨損量如圖6所示。由圖6可知，F(xiàn)e/WC試件總磨損量為12.94 mg，F(xiàn)e/WC/CeO2試件總磨損量為10.81 mg，F(xiàn)e/WC/CeO2試件總磨損量較Fe/WC降低了16%。

3.2.2 摩擦系數(shù)

圖7為試件摩擦系數(shù)隨時間變化圖。由圖7可知，F(xiàn)e/WC堆焊層平均摩擦系數(shù)為0.56，F(xiàn)e/WC/CeO2堆焊層平均摩擦系數(shù)為0.45。與Fe/WC堆焊層相比，F(xiàn)e/WC/CeO2堆焊層摩擦系數(shù)變化范圍較小，磨損曲線更加穩(wěn)定，具有更優(yōu)良的耐磨性能。CeO2提高了堆焊層熔池中流動性，提高了堆焊層致密性，改善堆焊層表面粗糙度，降低了堆焊層摩擦系數(shù)[26-27]。

分析認為，加入的CeO2稀土氧化物，提高了熔池中液態(tài)金屬流動性，一方面可使熔池中的氣體充分逸出，減小堆焊層中氣孔、夾雜等缺陷產(chǎn)生傾向，另一方面還可緩解堆焊快速升溫—快速冷卻產(chǎn)生的應力集中，從而減小堆焊層裂紋產(chǎn)生傾向；CeO2的細化晶粒和凈化晶界作用，可促進WC、M7C3、Cr23C6等硬質(zhì)相顆粒在堆焊層中的擴散并使其彌散分布，從而使得堆焊層致密性好、硬度高、表面粗糙度小、摩擦系數(shù)小、耐磨性高。

3.3 堆焊層沖擊韌性

利用JB-300B型沖擊試驗機測試Fe/WC、Fe/WC/CeO2堆焊層沖擊韌性。沖擊韌性測試時，沖擊能量150 J，擺錘預仰角150°，擺錘半徑750 mm，沖擊速度5.2 m/s，每種堆焊層取3個試樣。

圖8為試件沖擊韌性測試結(jié)果。由圖8可知，F(xiàn)e/WC堆焊層的沖擊韌性約為6.1 J/cm2，F(xiàn)e/WC/CeO2堆焊層沖擊韌性約為7.9 J/cm2。與Fe/WC堆焊層相比Fe/WC/CeO2堆焊層沖擊韌性提高了29%。CeO2作為稀土元素，可有效細化晶粒，使堆焊層中WC顆粒呈彌散分布，緩解因位錯滑移產(chǎn)生的位錯堆積[28-30]，有效避免堆焊層在沖擊力作用下產(chǎn)生的應力集中。此外，堆焊層中被細化的晶粒會形成密集分布的晶界，在晶界與共晶區(qū)聚集的WC顆粒，可阻礙裂紋沿晶擴展，改變裂紋擴展方向，增加裂紋擴展路徑，從而提高了Fe/WC/CeO2堆焊層的沖擊韌性。與本課題組前期制備的Fe-Cr-C-V堆焊層（7.5 J/cm2）[8]相比，F(xiàn)e/WC/CeO2堆焊層沖擊韌性提高了7%。

3.4 堆焊層耐蝕性

利用CS350型電化學工作站測試Fe/WC、Fe/WC/ CeO2堆焊層的電化學極化曲線來表征堆焊層耐蝕性。測試時，參比電極為飽和甘汞電極，輔助電極為鉑片，工作電極為暴露面積1 cm2的試樣，其他區(qū)域采用環(huán)氧樹脂進行密封，掃描速率1 mV/s，頻率為5 Hz。

圖9為Fe/WC、Fe/WC/CeO2試件動電位極化曲線圖。由圖9可知，F(xiàn)e/WC試件腐蝕電位為-0.54 V，F(xiàn)e/WC/CeO2試件腐蝕電位為-0.46 V，F(xiàn)e/WC/CeO2堆焊層腐蝕電位明顯大于Fe/WC堆焊層，腐蝕電位越大說明發(fā)生腐蝕的難度越大，受到腐蝕傾向較小，不易遭受腐蝕。與添加CeO2的堆焊層相比，未添加CeO2堆焊層孔隙較多，孔隙周圍產(chǎn)生一定腐蝕坑。縫隙腐蝕產(chǎn)物堆積在孔隙口，氧很難進入縫隙，而縫內(nèi)的氧難以得到補充，從而縫內(nèi)縫外就形成了一個小陽極大陰極的腐蝕電池[31-33]，表現(xiàn)為孔內(nèi)的金屬持續(xù)腐蝕，孔隙內(nèi)酸化，促使Cl離子進一步向縫隙內(nèi)遷移，由于自催化作用和酸化作用，腐蝕速度很快，耐腐蝕性能降低。CeO2的添加提高了堆焊層中碳化物硬質(zhì)相與粘結(jié)相的粘結(jié)性，提高涂層的致密性，降低了縫隙腐蝕產(chǎn)物生成，減少自催化和酸化作用提高了堆焊層耐腐蝕性能。

4 堆焊層使用性能評價

4.1 土槽試驗

利用自制的模擬土槽摩擦磨損試驗臺（如圖10）對比等離子堆焊Fe/WC、Fe/WC/CeO2旋耕刀與65Mn旋耕刀的耐磨性。

試驗時，各取40把65Mn（840℃淬火，540℃回火）材質(zhì)旋耕刀和等離子堆焊Fe/WC/CeO2旋耕刀，分5次（每次各8把）稱量后交錯裝夾在試驗機上。試驗機電機轉(zhuǎn)速60 r/min，旋耕刀回轉(zhuǎn)半徑110 cm。連續(xù)運轉(zhuǎn)24 h后將16把旋耕刀取下，洗凈吹干后利用珠恒ACS工業(yè)計數(shù)秤（15 kg/0.1 g）稱量。之后再各取40把等離子堆焊Fe/WC旋耕刀與等離子堆焊Fe/WC/CeO2旋耕刀稱量后分5次（每次各8把）交錯裝夾在試驗機上重復上述試驗。結(jié)果表明，F(xiàn)e/WC/CeO2堆焊層旋耕刀的平均磨損量（14.8 g）較65Mn 旋耕刀的磨損量（52.3 g）降低約71%，較Fe/WC堆焊層旋耕刀平均磨損質(zhì)量（17.8 g）降低了17%。

4.2 田間試驗

各取160把65Mn（840 ℃淬火，540 ℃回火）材質(zhì)的旋耕刀、等離子堆焊Fe/WC/CeO2旋耕刀，稱量后分5次（每次各32把）稱量后交錯安裝在1GKN-220 型旋耕機（每次裝夾64把）上進行田間試驗（如圖11），每次作業(yè)面積21.4 hm2后，取下旋耕刀并洗凈吹干后稱量計算磨損量平均值。然后再各取160把Fe/WC堆焊層旋耕刀、Fe/WC/CeO2堆焊層旋耕刀按照上述方法進行田間試驗并計算磨損量平均值。試驗地點：河北農(nóng)業(yè)大學試驗基地，機具前進速度4～5 km/h，土壤性質(zhì)為砂壤土，土壤堅實度308.82 kg/cm2，土壤含水率19%。

圖12為田間試驗前后的刀具磨損形貌，F(xiàn)e/WC堆焊層旋耕刀與Fe/WC/CeO2堆焊層旋耕刀磨損形貌無明顯差別。由圖12可見，65Mn旋耕刀的切刃部磨痕密集、明顯磨損；Fe/WC/CeO2堆焊層旋耕刀表面光潔，未發(fā)現(xiàn)明顯磨痕，堆焊層無脫落現(xiàn)象。Fe/WC/CeO2堆焊層旋耕刀平均磨損量（25 g）較65Mn旋耕刀（71 g）相比降低了65%，較Fe/WC堆焊層旋耕刀平均磨損質(zhì)量（29.5 g）降低了15%。添加的CeO2提高了堆焊層液態(tài)金屬流動性，降低了氣孔、裂紋等缺陷產(chǎn)生傾向，使堆焊層中硬質(zhì)相分布均勻，從而提高了Fe/WC/CeO2堆焊層旋耕刀耐磨性能。

土槽試驗和田間試驗結(jié)果表明，較65Mn旋耕刀相比，F(xiàn)e/WC/CeO2涂層旋耕刀耐磨性能更優(yōu)異。與本課題組前期制備的Fe-Cr-C-V堆焊層旋耕刀（32 g）相比[8]，平均磨損量降低了21%，F(xiàn)e/WC/CeO2堆焊層具有更加優(yōu)良的綜合性能。

5 結(jié) 論

1）采用正交試驗分析了堆焊電流、堆焊距離、堆焊速度、送粉速率對Fe/WC/、Fe/WC/CeO2堆焊層磨損量的影響，優(yōu)化了等離子堆焊工藝參數(shù)為：堆焊電流50 A，堆焊距離5 mm，堆焊速度15 cm/min，送粉速率25 g/min。

2）Fe/WC/CeO2等離子堆焊層與基體呈良好的冶金結(jié)合，堆焊層無明顯氣孔、裂紋等缺陷。與Fe/WC等離子堆焊層相比，F(xiàn)e/WC/CeO2堆焊層中硬質(zhì)相尺寸明顯減小，且呈彌散分布。

3）與Fe/WC等離子堆焊層相比，F(xiàn)e/WC/CeO2等離子堆焊層的硬度提高了22%、磨損量降低了16%、沖擊韌性提高了29%。田間試驗表明Fe/WC/CeO2堆焊層旋耕刀較常用65Mn旋耕刀平均磨損量降低了65%，較Fe/WC堆焊層旋耕刀平均磨損質(zhì)量降低了15%。

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Preparation and microstructure properties of Fe/WC/CeO2plasma surfacing layer for rotary blades

Hao Jianjun1,2,3, Zhan Zhiguo1, Hou Junying1,2, Zhao Jianguo1,2,3, Liu Jingchun1,2, Yin Changfeng4

(1.,,071001,; 2.,,g 071001,a; 3.,,g073000,a; 4..,.,261000,)

This study aims to improve the wear resistance, impact toughness, and free of frequent failure of contacting parts with soil in the agricultural machinery. A Fe/WC/CeO2ceramic composite coating was prepared on the Q235 steel substrate by plasma surfacing technology. An analysis was also made to clarify the influence of the CeO2compound on the wear resistance of Fe/WC cermet composite coating and the action mechanism. An orthogonal test was used to optimize the preparation process parameters of the Fe/WC/CeO2plasma surfacing layer, where the surfacing current, surfacing speed, powder feeding rate, and powder feeding distance were taken as the test factors and the wear quality as the evaluation index. Specifically, the welding current was 50 A, welding distance 5 mm, welding speed 15 cm/min, and power transport rate 25 g/min. The microstructure and phase composition of the surfacing layer were characterized by a scanning electron microscope, energy dispersive spectrometer (EDS), and X-ray diffractometer (XRD). The results showed that there was an outstanding interface between the surfacing layer and the matrix bonding zone, indicating that the surfacing layer and matrix permeated each other to form an excellent metallurgical bonding. The size of the hard phase in the surfacing layer decreased outstandingly in presence of a dispersion distribution, particularly with the shape like a fishbone, long rod, ball, and hexagonal. The surfacing layer was composed of γ-Fe, Fe-Cr-Ni solid solution, WC, M7C3, Cr7C3, Cr23C6, and W2C. The carbide hard phase (such as WC, Cr7C3,and Cr23C6) was effectively improved the hardness and wear resistance of the surfacing layer. In addition, the addition of CeO2decarbonized the WC hard phase to form W2C hard phase for better wear resistance. The Vickers microhardness tester, friction and wear testing machine and impact testing machine were used to measure the microhardness, wear resistance, and impact toughness of the surfacing layer. The corrosion resistance was also analyzed by an electrochemical workstation. It was found that there was a uniform distribution of microhardness with a gradual decrease from the coating to substrate along the section of the surfacing layer. The average microhardness of the Fe/WC/CeO2surfacing layer (HV0.5870) was much higher, indicating less wear quality, smaller friction coefficient, and better wear resistance, compared with the Fe/WC (HV0.5710). The reason was that the CeO2phase was evenly distributed to enhance the anti-wear properties, due to the refined hard phase, such as WC, M7C3,and Cr23C6in the surfacing layer. The impact toughness values of Fe/WC and Fe/WC/CeO2surfacing layers were about 6.1 J/cm2and 7.9 J/cm2, respectively. The average microhardness, impact toughness, and corrosion resistance of the Fe/WC/CeO2surfacing layer increased by 22%, 29%, and 15%, respectively, compared with Fe/WC. The soil groove test showed that the average wear of the Fe/WC/CeO2rotary blade was 71% lower than that of the commonly-used 65Mn rotary blade, and 17% lower than that of Fe/WC. The field experiments showed that the surface of the Fe/WC/CeO2layer was smooth with serious abrasion marks or falling off. The Fe/WC/CeO2coated rotary tillage knife (25 g) decreased by 65% and 15%, compared with the 65Mn rotary tillage knife (71 g), and Fe/WC coated rotary blade (29.5 g), respectively. Consequently, the Fe/WC/CeO2coating was prepared on the surface of agricultural machinery in contact with the soil by plasma surfacing, indicating a high application value with low cost, high efficiency, flexibility, and convenience. Anyway, the rotary tillage knife with the Fe/WC/CeO2coating surfacing layer can be expected to present an excellent wear resistance and comprehensive mechanical properties for agriculture production.

microstructure; performance; plasmasurfacing; surfacing layer; rotary blade

郝建軍，占志國，侯俊英，等. 旋耕刀Fe/WC/CeO2等離子堆焊層制備及其組織性能[J]. 農(nóng)業(yè)工程學報，2021，37(24)：1-8.doi：10.11975/j.issn.1002-6819.2021.24.001 http://www.tcsae.org

Hao Jianjun, Zhan Zhiguo, Hou Junying, et al. Preparation and microstructure properties of Fe/WC/CeO2plasma surfacing layer for rotary blades[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2021, 37(24): 1-8. (in Chinese with English abstract) doi：10.11975/j.issn.1002-6819.2021.24.001 http://www.tcsae.org

2021-08-26

2021-12-09

國家重點研發(fā)計劃（2017YFD0300907）

郝建軍，博士，教授，博士生導師，研究方向為農(nóng)業(yè)生產(chǎn)機械化自動化技術(shù)及裝備研發(fā)。Email：hjjpaper@163.com

10.11975/j.issn.1002-6819.2021.24.001

TG174.4

A

1002-6819(2021)-24-0001-08