2 </sub> of ZrO<sub> of spray of plasma of titanium alloy surface

Under The Condition Of Greater Thermal Shock Stress, the Coating Spalls Integrally From The Surface Of Ti-6Al-4V Substrate;Under The Condition Of Weaker Thermal Shock Stress, the Coating Fractures And Spalls Partly From The Surface Of The Substrate.

2 Ceramics Ni-base Alloy1 of Key Words Plasma Spraying Thermal Barrier Coatings Thermal Shock Property ZrO pottery and porcelain of foreword plasma spray - metallic gradient coating is Ying Hang coating of a kind of when the need that the hi-tech such as empty, spaceflight, enginery admits quickly comes out at be being developed in recent years new-style heat barrier, its composition (or group yuan) edge ply direction shows gradient to change distributing, the thermal stress that because temperature gradient is formed,can alleviate adequately [１ - 4] . Inspect the heatproof shake property of gradient coating, study failure mechanism of its thermal shock, distributing to optimizing the composition of gradient coating, develop the aftertreatment new technology of coating, the heatproof shake performance that improves coating further, lengthen its service life and enlarge its to apply limits to have important sense. The article discussed ZrO2 of spray of plasma of titanium alloy surface through heating up a loop to experiment - the heatproof shake behavior of NiCoCrAIY gradient coating. The article collects 2 experiments method to be in with law of atmosphere plasma spray preparation of surface of matrix of 5mm thick TC4(Ti-6Al-4V) the heat barrier coating of distributinging pattern of two kinds of part, say respectively for double deck coating (write down for DC) and gradient coating (write down for GC) , following watches are shown. Coating total ply is 1.

4mm left and right sides, among them each actual ply and the error control that design ply are in 0.

In 015mm. The ply of DC sample and GC sample is consistent, the purpose is have below same test condition can compare a gender. The group of coating of plasma spray heat barrier expresses coating structure ground floor into distributinging design the 2nd three-layer content of component of layer of the 4th the 5th surface (Vol%)100%N20%Z+N40%Z+N60%Z+N80%Z+N100%Z ply (Mm)GC0.

20.

20.

20.

20.

20.

4DC0.

6----0.

8 graphs 1 tensile strength checks methodological sketch map (A) bonding strength; (Drawing of 1- of B) cohesion intensity occasionally; 2- coating; 3- matrix grinds coating flank sample of smooth preparation metallographic, the organization that uses optical microscope to observe gradient coating distributings state. In Instron-1186 electron universal test machine has tensile test to two kinds of coating (experiment method shows) 1 times like the graph, determine the bonding strength of coating and matrix (the cohesion intensity of graph 1a) and coating (graph 1b) . Sample diameter is  φ 17mm, sample and drawing occasionally between with epoxy resin cementation. Use sample whole to heat, the hot loop means with cooling hardening undertakes thermal shock experiments, the thermal shock behavior that inspects gradient coating and double deck coating to fall in condition of temperature of different be heated. Part sample to be mixed at 700 ° C, 900 ° C, 1000 ° C, 1100 ° C hardening is taken out after 20min of heat preservation of 1200 ° C, till coating flakes,circulate repeatedly so or destroy, the record heats up circular time. Coating sample size is 15 × 8 × 6.

4 ｍ ｍ 3, use scanning report lens (SEM) and can chart appearance (the feature of thermal shock invalidation of ED) research coating. 3 results and analysis 3.

The macrostructure feature of 1 gradient coating pursues the 2 macroscopical metallographic that are gradient coating organize a photograph. Wrong department is TC4 matrix in the graph, the organization that white petitions in coating is NiCoCrAlY, grizzly organization is ZrO2. Come from matrix coating surface, along coating ply direction, the content of ZrO2 is added gradually much, the content of NiCoCrAlY criterion drop off, show group of successive gradient of yuan of composition to change distributing. And facing and metallic ground floor are expressed to be united in wedlock directly because of pottery and porcelain in double deck coating, cause in the mutation that there is composition in coating and the macroscopical interface that form from this, if pursue,3 are shown. This shows, composition gradient is changed distributing to change the macroscopical union way between coating into the microcosmic union means between spray particle, and its are microcosmic combinative interface dispersion distributings to become divisional territory at each in, from go up at all the composition in eliminating coating is jumped change phenomenon and the macroscopical union interface that cause from this. Graph 2 ZrO 2 - the sectional gold of coating of gradient of Y of ｌ of A of ｒ of C of ｏ of N ｉ C organizes photograph graph 3 ZrO 2 - the metallographic organization photograph of coating of double deck of Y of ｌ of A of ｒ of C of ｏ of N ｉ C pursues the tensile test result of coating of two kinds of 4 heat barrier 3.

The combinative strength that the combines intensity coating union strength of 2 gradient coating includes coating and matrix (namely bonding strength, record strength of the union between CS) and coating layer (namely cohesion intensity, write down AS) , used tensile test to undertake evaluating to the strength of two kinds of union of coating, if pursue,4 are shown. See by the graph, the strength of two kinds of union of gradient coating all the intensity of coating of prep above double deck. Cohesion intensity depends on the combinative strength of the particle between the layer, bonding strength depends on the combinative state of affairs of NiCoCrAlY particle and TC4 matrix, get the influence of leftover stress in coating. Composition gradient changes distributinging pass the time in a leisurely way besides the interface between the macroscopical layer in coating, with the physical property mutation that causes from this, because this improved the particle between the layer to join a state, alleviated the preparation stress in coating, make the combinative strength of coating is able to rise. The cohesion intensity value of two kinds of coating all is more than bonding strength value, and determine when bonding strength, outer add the effect that plays stress, the strain crack position of two kinds of coating all is in the combinative interface of coating and matrix, coating and matrix happening mechanism are separate, the combinative interface of ground floor of this specification NiCoCrAlY and titanium alloy matrix is whole coating - the weakest point in matrix system. 3.

The heatproof shake behavior of 3 gradient coating pursues the 5 heatproof shake that are coating of two kinds of heat barrier experiment circularly result. See by the graph, the coating of double deck of prep above of heatproof shake temperature of gradient coating, namely double deck coating is in the 1100 ° C, invalidation after circulating 1 times, and gradient coating is after 1 1200 ° C, loops just now invalidation; In identical thermal shock experiment temperature falls, the time of heatproof shake circulation of gradient coating is apparent coating of over double deck, and follow experiment temperature reduce, the increase with the markedder time of heatproof shake circulation of gradient coating, it is especially when experiment of 900 ° C, gradient coating experienced hot loop nearly 55 times rear ability invalidation, and double deck coating endured hot loop about 10 times merely namely invalidation. This shows, the coating of double deck of excel of heatproof shake function of gradient coating. The heatproof shake function of coating depends on the combinative strength of the size of the thermal stress in coating and coating [8] . In thermal shock experiment condition falls, the hot coefficient of expansion as a result of matrix of Y of ｌ of A of ｒ of C of ｏ of C of ｉ of ZrO2, N and TC4 is not identical, bring about the each part interior in coating to form thermal stress, form stress concentration on combinative interface. The composition of gradient coating shows gradient to change distributing, overcame the physical property between layer of surface of pottery and porcelain and metallic ground floor choppy phenomenon, alleviated the thermal stress in coating and interfacial stress concentration, accordingly its fight thermal shock function to be able to rise significantly [5] . Graph the result of thermal shock test of coating of two kinds of 5 heat barrier is additional, by the graph 5 still can see, the hot circulation time of two kinds of coating differs as the metabolic trend of experiment temperature, as experiment temperature elevatory, the circular time of double deck coating basically shows linear to reduce, and the circular time of gradient coating is shown nonlinear change. The means of thermal shock invalidation of likelihood and coating follows trend of this kind of change the change of temperature is concerned. Inside the experiment temperature limits of 900-1100 ° C, the invalidation kind of double deck coating did not produce change, all behave flake from matrix surface for coating whole, section relatively level off, show coating and matrix are mechanical depart. The invalidation manner of gradient coating varies along with the change of experiment temperature, when 1100 ° C and 1200 ° C experiment, gradient coating whole flakes from matrix surface, come off face level off, expression is the mechanical depart of coating and matrix; When 1000 ° C experiments, gradient coating also flakes from matrix surface, but its come off the face is uneven, expression produces coating and matrix machinery to depart for partial section, and the kind that expresses facing in order to tear off matrix happens another section section come off; When 900 ° C experiments, its invalidation kind produced bigger change, what expression is coating is fore-and-aft rupture to flake from matrix surface with one part coating, if pursue,6 are shown. The invalidation kind of gradient coating happens metabolic phenomenon along with the change of experiment temperature to mirror a coating to be when the action of the thermal shock stress that experiences different level, its invalidation behavior differs somewhat. Graph sample of 6 gradient coating experiments at 900 ° C the appearance of form of thermal shock invalidation when pursues 7 classics 900 ° C, the coating of gradient of appearance of sectional SEM form of coating of the gradient after 25 times heat circulates and matrix band section is when experiment of thermal shock of 900 ° C, its fight time of thermal shock circulation marked increase and area of elemental rich market was formed to concern in coating and matrix union interface. Graph 7 tie the SEM form appearance with sectional area for the coating after via 900 ° 25 C, heat circulate and matrix. See by the graph, after classics high temperature heats up a loop for many times repeatedly, both neither was formed to be the same as Yu Tu layer to organize in NiCoCrAlY ground floor and division of TC4 matrix union, also be different from the new look division that matrix organizes, use can chart appearance undertakes determining to the alloying element content of this area, its eventuate (At%):NI:48.

6% , ti:27.

4% , al:10.

1% , cr: 8.

2% , co: 0.

9% , y: 0.

35% , v: 0.

4% , foreign matter (Fe, the) such as Si: The others. It is thus clear that this area contains a lot ofelemental Ni, Ti and Al to wait, after this shows gradient coating heats up a loop for long via 900 ° C, niCoCrAlY ground floor and TC4 alloy matrix produced hot interaction. This kind of hot interaction improved the combinative condition of coating and matrix, increased the combinative strength of coating and matrix, improved the heatproof shake performance of coating thereby. 4 conclusion (1)ZrO 2 - the composition of coating of gradient of Y of ｌ of A of ｒ of C of ｏ of N ｉ C shows successive gradient to change distributing, the composition in eliminating double deck coating is jumped change phenomenon and the macroscopical union interface that cause from this, increased the cohesion strength of the bonding strength of coating and matrix and coating, its fight coating of double deck of excel of thermal shock function. (2)ZrO 2 - the means of thermal shock invalidation of coating of gradient of Y of ｌ of A of ｒ of C of ｏ of N ｉ C follows experiment temperature change and change somewhat. Below action of stress of bigger thermal shock, coating whole flakes from matrix surface and invalidation; Below stress of lesser thermal shock, produced hot interaction as a result of ground floor of Y of ｌ of A of ｒ of C of ｏ of N ｉ C and TC4 alloy matrix, improved the combinative condition of coating and matrix, coating is fore-and-aft rupture and flake from matrix surface partly and invalidation. CNC Milling CNC Machining